SQL Notes

sqlnotes.htm; updated 2/22/01

STRUCTURED QUERY LANGUAGE (SQL)

Introduction.

The Oracle RDBMS is available on many different operating system platforms including Windows and UNIX.
Oracle is a relational DBMS - even the data dictionary is simply a collection of tables of data along with indexes and other objects such as sequences and triggers.
SQL has a basic grammar and syntax.
The functionally of the SQL language is virtually identical across these operating system platforms.
Using SQL does not require programming experience, but programming experience can help you conceptualize what a particular SQL command will accomplish.
The keywords for SQL queries that retrieve data are SELECT, FROM, WHERE, and ORDER BY. Other command options also exist, but these are the basic ones.

Connecting to the ORACLE Database.

Directions for connecting to the ORACLE database are given in the web handout, Getting Started with Oracle that is available on the course web site.

Naming Difficulties.

When building a schema (meaning the definition of the tables, indexes, and other objects that comprise a database), it is important to name objects like tables, columns, indexes with meaningful names. A failure to follow this naming rule can result in difficulties for users when they are creating queries.
Oracle allows object names to be up to 30 characters long. Make use of this capability.
Here are some rules to follow.

Don't abbreviate unless it is necessary. Example, it is better to name a column WorkerName than Wname.
Be consistent when abbreviating. Don't use EmpNo in one table and Eno in another table and EmpNumber in still another table.
The Purpose or Meaning of a column or table must be apparent from the name. What would be the meaning of a table named Scde (Storage Code)? A better name would be STORAGECODE.
If you use Underscores as part of a naming convention, then be consistent. If you are not consistent, then no one can remember when to use them and when not to use them.
Be consistent in using Plurals. Is the name of that table "EMP" or "EMPS"? Is it "NOTE" or "NOTES"?

SQL BASIC INFORMATION

SQL and UNIX Syntax.

The SQL syntax used in these notes complies with Oracle’s SQL*PLUS product.
UNIX syntax used in these notes complies with most UNIX operating systems.
The American National Standards Institute (ANSI) first published ANSI SQL standards in 1986.
Oracle Corporation - provides SQL*PLUS (an enhanced version of SQL) as part of the Oracle RDBMS product. This means that SQL*PLUS has some non-ANSI standard SQL commands that will not run on other RDBMS platforms.
Microsoft Corporation - provides the SQL Server RDBMS software -- a competitor with Oracle Corporation.

SQL Standards - Their Characteristics and Benefits.

The ANSI SQL Standard provides:

Specific syntax and semantics of SQL data definition and datamanipulation languages.
Basic data structures and operations for designing, assessing, maintaining, controlling, and protecting an SQL database.
Portability of applications and database definition. Easy to move applications from one machine to another.
Minimal standards for adoption among products claiming to be SQL compatible.

Reduced training costs - IS professionals share a common language.
Productivity - IS professionals can become proficient in its use.
Application longevity - A language tends to remain standard for a long time.
Reduced dependence on a single vendor.

SQL Data Types.

Data stored in a relational database can be stored using a variety of data types. The primary ORACLE data types are NUMBER, VARCHAR, and CHAR for storing numbers anda text data; however, there are additional data types that are supported to support backward compatability with products.given below:

KEY DATA TYPES
CHAR(size)	Fixed-length character data, size characters long. Maximum size=255; default=1 byte. Padded on right with blanks to full length of size.
DATE	Valid dates range from Jan 1, 4712 B.C. to Dec 31, 4712 A.D.
NUMBER	For NUMBER column with space for 40 digits, plus space for a decimal point and sign. Numbers may be expressed in two ways: first, with numbers 0 to 9, the signs + and -, and a decimal point(.); second, in scientific notation, e.g. 1.85E3 for 1850. Valid values are 0 and positive and negative numbers from 1.0E-130 to 9.99…E125.
VARCHAR2(size)	Variable length character string, maximum size up to 2000 bytes.
MISCELLANEOUS DATA TYPES AND VARIATIONS
DECIMAL	Same as NUMBER.
FLOAT	Same as NUMBER.
INTEGER	Same as NUMBER.
INTEGER(size)	Integer of specified size digits wide; same as NUMBER(size) of specific size digits wide.
LONG	Character data of variable size up to 2Gb in length. Only one LONG column may be defined per table. LONG columns may not be used in subqueries, functions, expressions, where clauses, or indexes. A table containing LONG data may not be clustered.
LONG RAW	Raw binary data; otherwise the same as LONG (used for images).
LONG VARCHAR	Same as LONG
NUMBER(size)	For NUMBER column of specified size in digits.
NUMBER(size,d)	For NUMBER column of specified size with d digits after the decimal point, e.g. NUMBER(5,2) could contain nothing larger than 999.99 without an error being generated.
NUMBER(*)	Same as NUMBER.
SMALLINT	Same as NUMBER.
RAW(size)	Raw binary data, size bytes long, maximum size=255 bytes.
ROWID	A value that uniquely identifies a row in an Oracle database - it is returned by the pseudo-column ROWID. Table columns may not be assigned this type.
VARCHAR(size)	Same as VARCHAR2. Always use VARCHAR2.

SQL and SQLPLUS Basics and Error Messages.

We have already seen that SQL can be used to select data.
SQL is used for data manipulation in terms of adding, updating, or deleting data.
The primary verbs for data manipulation are insert, update, or delete data.
Taken together, these are the four primary verbs you use in SQL.
We will start learning to write SQL commands by connecting through a telnet session to connect to the ORACLE database, and then by using the SQLPLUS command to enter the SQLPLUS environment.
Start using SQLPLUS by typing the command at the prompt SQLPLUS (or by using the appropriate graphical user interface if it is provided). The typical prompt you receive is: SQL >
Sometimes your connection will fail and you will receive an error message.

If you get the following errors, it may be that access to the ORACLE binary files is not available because the PATH command for your account is incorrectly established - see your instructor to correct this.
The problem could also be that the database has been shutdown and so ORACLE is not running.
ERROR: ORA-1017: invalid username/password; logon denied. Unable to CONNECT to ORACLE after 3 attempts, exiting SQL*Plus

When you are finished with your work, you quit SQLPLUS with the QUIT or EXIT command.

Case in Names and Data.

Oracle ignores case (upper versus lower case letters) when you type table and column names. It converts table and column names to uppercase when you type a query and checks the query's validity in the data dictionary.

Data, however, may be stored as a combination of upper and lower case. You can use Oracle functions to convert data between upper and lower case if that becomes necessary as part of a programming application.

Case matters only if SQLPLUS is checking a value for equality in the database. For example, the following conditions are not identical.

Where Section = 'f'
Where Section = 'F'

Here the values "f" and "F" inside quotes are called literals, meaning literal values.

SELECT QUERIES

SQL Query Suntax.

This section teaches you to write a number of different types of SQL queries.
SQL is based on the data transform language first named SEQUEL.
This is a relational calculus type of language which provides three capabilities in a very simple syntax.
The basic syntax as we have already seen is:

SELECT (column list)
FROM (table list)
WHERE (condition clause)

A Sample Query.

This result comes from the ORACLE database which is in use at SIUE. This database contains all tables given in the Oracle Press: The Complete Reference, but you do not need to have this book in order to use this set of notes.

SQL> Select City, Temperature, Humidity from WEATHER
2 where Temperature > 80 and Humidity < 90
3 order by Temperature ;

CITY        TEMPERATURE HUMIDITY
----------- ----------- ----------
PARIS       81          62
ATHENS      97          89

Describing a Table.

Often it is useful to be able to describe the structure of a table because you may not be familiar with a particular table.
The Describe command is used to accomplish this. This example gives the description of the WEATHER and LOCATION tables in the ORACLE database.

SQL> describe weather;
Name            Null?    Type
--------------- -------- ----
CITY                     VARCHAR2(11)
TEMPERATURE              NUMBER
HUMIDITY                 NUMBER
CONDITION                VARCHAR2(9)

SQL> describe location;
Name            Null?    Type
--------------- -------- ----
CITY                     VARCHAR2(25)
COUNTRY                  VARCHAR2(25)
CONTINENT                VARCHAR2(25)
LATITUDE                 NUMBER
NORTHSOUTH               CHAR(1)
LONGITUDE                NUMBER
EASTWEST                 CHAR(1)

Result of a SELECT Command.

The SELECT command produces a "virtual table" -- this is a combination of columns and rows from one or more selected tables given in the query. This normally produces a subset of the columns and rows that comprise the tables in the query.
The virtual table produced by a query is stored on disk in a Temporary tablespace area or in RAM that is sometimes called a "scratch" space because it is used over and over. The actual location of the virtual table is a function of the size of the table.
When the virtual table is no longer needed, Oracle disposes of it.
The basic operation of each of the three components of the SELECT command are explained below.

SELECT	List the columns including expressions involving columns from base tables or views to be projected into the table that will be the result of the command.
FROM	Identifies the tables or views from which columns will be chosen to appear in the result table. This must also list the tables or views needed to join tables to process the query.
WHERE	Includes conditions that restrict the rows selected as well as the conditions for joining two or more tables or views.

THE COMMUNITY HOSPITAL
EXAMPLE DATABASE

The table examples given below assume the database schema represented by the ER diagram given here. The ER diagram only shows primary key attributes.

BILLED

BILL_NO NUMBER(5) - PRI KEY

PATIENT_NO NUMBER(9)

ITEM_CODE NUMBER(5)

CHARGE NUMBER(7,2)

TREATS

PHY_ID NUMBER(4) - PRI KEY

PATIENT_NO NUMBER(4) - PRI KEY

PROCEDURE_NO NUMBER(4) - PRI KEY

DATE_TREATED DATE - PRI KEY

TREAT_RESULT VARCHAR2(50)

ITEM

ITEM_CODE NUMBER(4) - PRI KEY

DESCRIPTION VARCHAR2(50)

NORMAL_CHARGE NUMBER(7,2)

PHYSICIANS

PHY_ID NUMBER(4) - PRI KEY

PHY_PHONE CHAR(8)

PHY_NAME VARCHAR2(50)

PATIENT

PATIENT_NO NUMBER(4) - PRI KEY

DATE_LAST_TREATED DATE

PAT_NAME VARCHAR2(50)

ROOM_LOCATION CHAR(4)

ROOM

ROOM_LOCATION CHAR(4) - PRI KEY

ROOM_ACCOMODATION CHAR(2)

ROOM_EXTENSION NUMBER(4)

PROCEDURES

PROCEDURE_NO NUMBER(4) - PRI KEY

PROC_DESCRIPTION VARCHAR2(50)

EXAMPLE #1 – SIMPLE SELECT TO RETURN A SET OF ROWS BASED ON A SIMPLE SINGLE VALUE IN THE WHERE CLAUSE.

Consider the table named BILLED as defined above. The command to select the PATIENT_NO, ITEM_CODE, and CHARGE and from the BILLED table for a specific PATIENT_NO is:

SELECT patient_no, item_code, charge
FROM billed
WHERE patient_no = 1117;

PATIENT_NO ITEM_CODE     CHARGE
---------- ---------- ----------
      1117       2222       7.54
      1117       2255         25

Notice the SELECT clause always ends in the semi-colon.

EXAMPLE #2 – ELIMINATE DUPLICATE ROWS.

To eliminate duplicate rows in order to display just distinct rows, the SELECT DISTINCT command may be used. This gives all of the different charges that are stored to the table.

SELECT DISTINCT charge
FROM billed;

    CHARGE
----------
      2.21
      4.56
      6.68
      7.54
      7.75
        25
...not all rows are displayed here.

EXAMPLE #3 – SIMPLEST QUERY DISPLAYS ALL COLUMNS IN A TABLE.

To display all columns from the BILLED table use the wildcard *.

SELECT *
FROM billed
WHERE patient_no = 1116;

PATIENT_NO ITEM_CODE     CHARGE
---------- ---------- ----------
      1116       2242       4.56
      1116       2243       6.68

EXAMPLE #4 – QUERY DISPLAYS ALL COLUMNS AND ROWS.

To display all columns and all rows from the BILLED table eliminate the WHERE clause.

SELECT *
FROM billed ;

PATIENT_NO ITEM_CODE     CHARGE
---------- ---------- ----------
      1117       2222       7.54
      1113       2233       2.21
      1117       2255         25
      1113       2222       7.75
      1115       2245        175
...not all rows are displayed here.

ARITHMETIC, LOGICAL, AND OTHER OPERATORS.

The various arithmetic, logical, and additional operators are shown in the table below.
Examples using some of the operators are provided after the table.
Arithmetic operators are used to qualify expressions in WHERE clauses.
There are operators such as LIKE for performing character string pattern matching.
The IS NULL and IS NOT NULL operators are used to see if data exists in a row - a column that is completely empty is NULL. The word IS is required.
The logical operators AND, OR, and NOT may be used to create complicated WHERE clauses. You may use parentheses to group logical operators properly.

**ARITHMETIC OPERATORS**
Page = 6	Page is equal to 6
Page > 6	Page is greater than 6
Page >= 6	Page is greater than or equal to 6
Page < 6	Page is less than 6
Page <= 6	Page is less than or equal to 6
Page != 6 or Page ^= 6 or Page <> 6	Page is not equal to 6

**USING THE LIKE OPERATOR**
Feature LIKE ‘Mo%’	Feature begins with the letters Mo. Note the % wildcard represents any number of spaces or characters.
Feature LIKE ‘_ _I%’	Feature has the letter I in the third position. Note the underline (_) represents one space.

**USING THE IS NULL and IS NOT NULL OPERATORS**
Precipitation IS NULL	The column named Precipitation contains no value or is unknown.
Precipitation IS NOT NULL	The column named Precipitation contains some value or is known.

**USING THE IN and BETWEEN OPERATORS**
Page IN (1,2,3)Page is in the list (1,2,3)
Page BETWEEN 6 AND 10	Page is equal to 6, 10, or anything in between.
Section IN (‘A’, ‘B’, ‘F’)	Section is in the list (A, B, or F ) Note use of ‘’ quotes.

**USING LOGICAL OPERATORS – OR, AND, NOT**
Section = ‘A’ OR Section = ‘B’	The value of the column Section is either A or B for this to evaluate to TRUE.
Section = ‘A’ AND Page > 2	The value of the column Section must be A and the value of the column Page must be greater than 2 for this to evaluate to TRUE.
NOT Section = ‘A’	Section must have some value other than A for this to evaluate to TRUE.

EXAMPLE #5 – USES LOGICAL AND OPERATOR.

To display all charges greater than $5.00 for the PATIENT_NO 1116.

SELECT charge
FROM billed
WHERE patient_no = 1116 AND charge > 5.00;

CHARGE
----------
6.68

EXAMPLE #6 – USES LOGICAL OR OPERATOR.

To display all charges for either patient 1116 or patient 1117.

SELECT patient_no, charge
FROM billed
WHERE patient_no = 1116 OR patient_no = 1117;

PATIENT_NO     CHARGE
---------- ----------
      1117       7.54
      1117         25
      1116       4.56
      1116       6.68
      1117     167.67
      1117     222.21
      1117       4.92

EXAMPLE #7 – USES COUNT FUNCTION.

SQL provides many built-in functions (such as COUNT, MAX, MIN, SUM, and AVG) to be used as operators for columns.
An example of counting the number of times patient 1116 has been charged for items. This counts the number of rows for the patient.

SELECT COUNT(*)
FROM billed
WHERE patient_no = 1116;

COUNT(*)
---------
2

EXAMPLE #8 – DISPLAYS DISTINCT ROWS – ELIMINATES DUPLICATE ROWS ON THE OUTPUT.

Suppose you want the number of DISTINCT procedures performed on a patient. This counts the number of distinct values that appear in the column named PROCEDURE_NO for the patient.

SELECT COUNT ( DISTINCT procedure_no )
FROM treats
WHERE patient_no = 1113;

COUNT(DISTINCTPROCEDURE_NO)
---------------------------
2

EXAMPLE #9 – SPECIFY MEANINGFUL COLUMN NAMES.

To "jazz up" the output, you may specify creative column names to appear at the top of a column of output.
The default is to list the column name above the column.

SELECT COUNT (DISTINCT procedure_no) AS "No. of Procedures"
FROM treats
WHERE patient_no = 1113;

No. of Procedures
-----------------
2

DISPLAYING CONSTANTS AND CALCULATED VALUES

Before using data aggregate functions such as COUNT or SUM, you should understand that you cannot mix row-level data output in the same SELECT clause with data aggregate functions.

EXAMPLE #10.

To display a calculated value such as the current charge and the amount that would be charged if the charge were increased by 6% for all rows in the ITEM table, the command is:

SELECT normal_charge, normal_charge*1.06
FROM item;

NORMAL_CHARGE NORMAL_CHARGE*1.06
------------- ------------------
         7.54             7.9924
         2.21             2.3426
          4.5               4.77
       284.59           301.6654
           25               26.5
...not all items are listed here.

EXAMPLE #11.

To compute how long a patient was in the hospital, you can perform arithmetic operations on both numeric as well as date type data.
The example below shows the use of date type data to list all patients hospitalized more than 6 days. This also shows an example of using an arithmetic expression in a WHERE clause.

SELECT patient_no, date_discharged, date_admitted,
(date_discharged - date_admitted + 1)
As "No. of Days In"
FROM patient
WHERE (date_discharged - date_admitted + 1 ) > 6;

PATIENT_NO DATE_DISC DATE_ADMI No. of Days In
---------- --------- --------- --------------
      1117 22-DEC-01 16-DEC-01              7
      1114 24-DEC-01 15-DEC-01             10
      1115 25-DEC-01 15-DEC-01             11

SORTING, GROUPING and the BETWEEN OPERATOR

EXAMPLE #12 – USING SORTING AND GROUPING.

The ORDER BY optional clause will sort results in either ascending or descending order. The optional clause for descending is DESC.
The GROUP BY optional clause is used to group rows with common values.
The example below produces a list of the total charges per patient for expensive medical items (CHARGE greater than $100 for an item) where patients owe the hospital a sum (total charges over $500).
Also note that we can only include column data such as the PATIENT_NO and aggregate data such as SUM(CHARGE) together in a query when we use the GROUP BY clause.
The BETWEEN operator is used to simplify query writing for a range of qualifications, for example, when a value is BETWEEN x and y, using the BETWEEN x and y is equivalent to saying the value is >=x AND =<y.

SELECT patient_no, SUM(charge)
FROM billed
WHERE (patient_no BETWEEN 1110 AND 1200) AND
charge > 100
GROUP BY patient_no
HAVING SUM(charge) > 200
ORDER BY patient_no;

PATIENT_NO SUM(CHARGE)
---------- -----------
1112 782.55
1117 389.88

The GROUP BY specifies control breaks for subtotals.
The HAVING clause must be used because the group-level data is aggregated.
The HAVING clause is like WHERE but must be used when the condition involves group-level data.

EXAMPLE #13 – MAJOR AND MINOR SORTS.

You can sort by more than one variable (major and minor sort).
The query below shows the results in descending total charge sequence (use of the DESC option since the default is ascending), then by ascending PATIENT_NO as the minor sort variable.

SELECT patient_no, SUM(charge) total_charge
FROM billed
WHERE (patient_no BETWEEN 1110 AND 1200) AND
charge > 100
GROUP BY patient_no
HAVING SUM(charge) > 50
ORDER BY total_charge DESC, patient_no;

PATIENT_NO TOTAL_CHARGE
---------- ------------
      1112       782.55
      1117       389.88
      1115          175

EXAMPLE #14 – ANOTHER BETWEEN EXAMPLE.

This is another example of the BETWEEN operator and lists all patients who were charged between $160 and $170 for item 2245.
The second query shows all charges for item 2245.

SELECT patient_no, charge
FROM billed
WHERE item_code = 2245 AND
charge BETWEEN 160 AND 170;

PATIENT_NO     CHARGE
---------- ----------
      1112     167.67
      1112     167.67
      1117     167.67

SELECT patient_no, charge
FROM billed
WHERE item_code = 2245;

PATIENT_NO     CHARGE
---------- ----------
      1115        175
      1112     167.67
      1112     167.67
      1117     167.67

THE IN OPERATOR

The IN operator may be used to replace the OR operator to simplify a query.
Later you will see examples where IN must be used for complex queries.

EXAMPLE #15 – USING THE IN OPERATOR.

This example lists the patients who had either Dr. Hawkeye Pierce or Dr. Trapper John or Dr. Jonas Salkman as a physician.

SELECT DISTINCT patient_no, phy_id
FROM treats
WHERE phy_id IN
(8887, 8886, 8882);

PATIENT_NO     PHY_ID
---------- ----------
      1112       8887
      1113       8882
      1113       8887
      1115       8886
      1116       8886
      1117       8887

It would be nice to show the patient names (PAT_NAME field) and associated physician names (PHY_NAME field) along with the Patient information. We shall see how to accomplish this in the next section.

MULTIPLE TABLE QUERIES

SQL can produce data from several related tables by performing either a physical or virtual join of the tables. The default is a virtual join.
The WHERE clause is most often used to perform the JOIN function where two or more tables have common columns such as is the case for the PATIENT and BILLED tables.

EQUI-JOIN and NATURAL JOIN

The Equi-Join and Natural Join are equivalent except that duplicate columns are eliminated in the Natural Join that would otherwise appear in the Equi-Join.
Recall the immediate example above where the query listed the PATIENT_NO and PHY_ID, but not the PAT_NAME or PHY_NAME fields. This query joints the PATIENT, PHYSICIAN, and TREATS tables to produce the desired information.
The query also demonstrates the use of an ALIAS for a table name - here we have three aliases (PA, PH, and TR), one for each table.
When two or more tables have a column with the same name, the name can be qualified by using the table name combined with the period (.) in referring to the column, e.g. billed.patient_no. Note that columns with unique names do not have to be qualified by the table name.
The COLUMN commands given prior to the SELECT are used to format the output.

EXAMPLE #16a – JOIN THREE TABLES.

COLUMN pat_name FORMAT A18;
COLUMN phy_name FORMAT A18;
SELECT DISTINCT PA.patient_no, pat_name, PH.phy_id, phy_name
FROM patient PA, physician PH, treats TR
WHERE PA.patient_no = TR.patient_no AND
PH.phy_id = TR.phy_id AND
PH.phy_id IN (8887, 8886, 8882);

PATIENT_NO PAT_NAME           PHY_ID PHY_NAME
---------- ------------------ ------ ------------------
      1112 Eminem               8887 Dr. Hawkeye Pierce
      1113 George Marshall      8882 Dr. Jonas Salkman
      1113 George Marshall      8887 Dr. Hawkeye Pierce
      1115 Barbara Streisand    8886 Dr. Trapper John
      1116 G. W. Bush           8886 Dr. Trapper John
      1117 Sally Field          8887 Dr. Hawkeye Pierce

The next example below shows the PATIENT_NO and DATE_DISCHARGED from the PATIENT table and the associated CHARGE from the BILLED table.
The sequence of table names in the FROM list is immaterial. If a column is indexed, the DBMS will automatically optimize the use of the index in parsing the query.

EXAMPLE #16b – JOIN TWO TABLES.

SELECT billed.patient_no, date_discharged, charge
FROM billed, patient
WHERE patient.patient_no = billed.patient_no;

PATIENT_NO DATE_DISC     CHARGE
---------- --------- ----------
      1117 22-DEC-01       7.54
      1113 21-DEC-01       2.21
      1117 22-DEC-01         25
      1113 21-DEC-01       7.75
      1115 25-DEC-01        175
      1116 22-DEC-01       4.56
...not all of the rows are shown here.

OUTER JOIN and TABLE NAME ALIASES (ABBREVIATIONS)

There may be situations where a row in one table, such as a PATIENT table has no corresponding rows in another table such as the CHARGE table (the patient has not yet incurred any charges - a most unusual circumstance in any hospital).
The JOIN of these tables will produce rows where some columns have NULL values. This is called the Outer Join. The Oracle RDBMS supports Outer Joins.

EXAMPLE #17 – OUTER JOIN and USING ALIAS.

The following command might produce the sample table shown after the command.
This example also shows another example of using "alias" names for tables in order to shorten the query that is written.
Here the alias for BILLED has been shortened to the letter "B" and PATIENT to "P".
Note the resulting NULL cells for some rows.
The (+) for the table for which there will be NULL values in terms of matching the P.PATIENT_NO to the B.PATIENT_NO is required.

SELECT p.patient_no, b.charge
FROM billed b, patient p
WHERE p.patient_no = b.patient_no(+);

PATIENT_NO     CHARGE
---------- ----------
      1111
      1112        225
      1112     167.67
      1112     167.67
      1112       4.92
      1112     222.21
      1113       2.21
      1113       7.75
      1114
      1115        175
      1116       4.56
...not all rows are shown here.

If we only want a list of patients who have no charges yet, the following query with a WHERE clause testing for NULL values will work. Note that this result is a subset of the above result.

SELECT p.patient_no, b.charge
FROM billed b, patient p
WHERE p.patient_no = b.patient_no(+) AND
b.charge IS NULL;

PATIENT_NO     CHARGE
---------- ----------
      1111
      1114

SUBQUERIES

The object of a WHERE clause can be another SELECT query.
Sometimes this makes it simpler to write a query that would otherwise have a very complex WHERE clause.
The two queries shown in the example below are equivalent. Both queries produce a list of ITEM_CODEs and the associated description of the items for a specific patient. To produce the list the ITEM and BILLED tables must be joined.

EXAMPLE #18 – A COMPLEX QUERY AND THE SUBQUERY.

SELECT item.item_code, description
FROM item, billed
WHERE item.item_code = billed.item_code AND
patient_no = 1116;

ITEM_CODE DESCRIPTION
---------- ----------------
2242 4 inch dressing
2243 Syringe, 8 gauge

SELECT item_code, description
FROM item
WHERE item_code IN
(SELECT item_code FROM billed
WHERE patient_no = 1116);

ITEM_CODE DESCRIPTION
--------- ----------------
2242 4 inch dressing
2243 Syringe, 8 gauge

EXAMPLE #19 – USING IN WITH THE SUBQUERY.

When an inner query (subquery) returns a set or list of values, we can use the IN operator to match on equality conditions.
In fact, the IN operator was used for the above as shown here.

SELECT item_code, description
FROM item
WHERE item_code IN
(SELECT item_code FROM billed
WHERE patient_no = 1116);

There are many other types of subqueries. You can spend many weeks studying the topic of SQL query writing.

VIEW DEFINITION

A VIEW is a virtual table that does not exist in reality, but is a logical definition of a set of related columns, usually from multiple tables.
A VIEW presents data to the end user of an application system the way that the end user is used to seeing the data.

For example, the Customer Order Form is a view of data from several different tables including CUSTOMER, ORDERS, PRODUCT, ORDERLINE, and SALESPERSON.

A VIEW can also be used to simplify query generation and to add data security to a database by limiting the data that an end user can access.
A VIEW definition is permanently stored as part of the database.
The example below creates a view named PATIENT_BILL that includes the PATIENT_NO, ITEM_CODE and CHARGE columns from the BILLED table and the DESCRIPTION column from the ITEM table, and the DATE_DISCHARGED from the PATIENT table.

EXAMPLE #20 – CREATE A VIEW.

CREATE VIEW patient_bill AS
    SELECT B.patient_no, P.pat_name,
        B.item_code, charge,
        description, date_discharged
    FROM patient P, billed B, item I
    WHERE P.patient_no = B.patient_no AND
        I.item_code = B.item_code;

View created.

Note that the relationship from PATIENT to BILLED is 1:N and the relationship from ITEM to BILLED is 1:N.
In other words, the BILLED table is the intersection table linking PATIENT and ITEM.
Now you can query the view PATIENT_BILL just as you would a table. When you execute the query, the view is generated by the DBMS and loaded with data, then your query is executed.

Column Description Format A22;
SELECT patient_no, item_code, charge,
        description
    FROM patient_bill
    WHERE patient_no = 1117;

PATIENT_NO ITEM_CODE   CHARGE DESCRIPTION
---------- --------- -------- ---------------------
      1117      2222     7.54 Syringe, 19 gauge
      1117      2255       25 Saline Soln, 1 liter
      1117      2245   167.67 Surgical Prep Pack #8
      1117      2224   222.21 Surgical Prep Pack #4
      1117      2267     4.92 Bed Pan

DERIVED COLUMNS

A view may contain derived (or virtual) columns.
For example, the total charges by patient for room and special items in a room (item codes between 2200 and 2250).
A view for this aggregate data can be created from the PATIENT_BILL view that was created in the example above.
The new view (code shown below for this view of a view) named ROOM_CHARGE has two virtual columns named OCCUPANT and ROOM_CHGS.
Note that ROOM_CHARGES is the sum of the charges for an occupant of the room.

EXAMPLE #21 – DERIVED COLUMNS.

CREATE VIEW room_charge (occupant, room_chgs) AS
    SELECT pat_name, sum(CHARGE)
    FROM patient_bill
    WHERE item_code BETWEEN 2200 AND 2250
    GROUP BY pat_name;

EXAMPLE #21 – SELECTING FROM A VIEW.

Now you can select charges for an occupant with the simple query given below.

Column occupant Format A20;
SELECT occupant, room_chgs
    FROM room_charge
    WHERE room_chgs > 100;

OCCUPANT              ROOM_CHGS
-------------------- ----------
Barbara Streisand           175
Eminem                   782.55
Sally Field              397.42
which is equivalent to: SELECT pat_name, SUM(charge)
    FROM patient_bill
    WHERE item_code BETWEEN 2200 AND 2250
    GROUP BY pat_name
    HAVING SUM(charge) > 100;

PAT_NAME             SUM(charge)
-------------------- -----------
Barbara Streisand            175
Eminem                    782.55
Sally Field               397.42

Attached here is the Script file used to create and populate the tables used in this handout. They files assume the existence of the DATA tablespace and the DATA_INDEX tablespace for storage of tables and indexes. The user account assumed is named DBOCK. If you run the script to create the tables with data in your own Oracle account, replace the name of the user account with your own account name. Do not attempt to create the PUBLIC SYNONYMS since these already exist for the DBOCK account.

REM Table ROOM
        drop table ROOM;
        create table ROOM (
          ROOM_LOCATION char(4)
            constraint PK_ROOM primary key
              using index tablespace DATA_INDEX
              pctfree 5,
          ROOM_ACCOMMODATION char(2)
            constraint NN_ACCOMMODATION NOT NULL,
          ROOM_EXTENSION      number(4) default NULL
    )
        tablespace DATA;

Insert into ROOM values ('GM01', 'P2', 1111);
Insert into ROOM values ('GM02', 'P2', 1112);
Insert into ROOM values ('GM03', 'P2', 1113);
Insert into ROOM values ('GM04', 'P2', 1114);
Insert into ROOM values ('IC01', 'P1', 2221);
Insert into ROOM values ('IC02', 'P1', 2222);
Insert into ROOM values ('IC03', 'P1', 2223);

REM Table PATIENT
        drop table PATIENT;
        create table PATIENT (
          PATIENT_NO        number(4)
            constraint PK_PATIENT primary key
              using index tablespace DATA_INDEX
              pctfree 5,
          DATE_ADMITTED     date default sysdate
            constraint NN_DATE_ADMITTED NOT NULL,
          DATE_DISCHARGED   date default NULL,
          PAT_NAME          varchar2(50)
            constraint NN_PAT_NAME NOT NULL,
          ROOM_LOCATION     char(4)
            constraint NN_ROOM_LOCATION NOT NULL,
       constraint FK_PATIENT_ROOM foreign key (ROOM_LOCATION)
          references ROOM
          on delete cascade
    )
        tablespace DATA;

Insert into PATIENT values (1111, '15-DEC-01', '20-DEC-01', 'Tom Thumb', 'GM03');
Insert into PATIENT values (1117, '16-DEC-01', '22-DEC-01', 'Sally Field', 'GM01');
Insert into PATIENT values (1113, '17-DEC-01', '21-DEC-01', 'George Marshall', 'GM03');
Insert into PATIENT values (1114, '15-DEC-01', '24-DEC-01', 'William Clinton', 'GM02');
Insert into PATIENT values (1116, '18-DEC-01', '22-DEC-01', 'G. W. Bush', 'IC01');
Insert into PATIENT values (1115, '15-DEC-01', '25-DEC-01', 'Barbara Streisand', 'IC03');
Insert into PATIENT values (1112, '18-DEC-01', '20-DEC-01', 'Eminem', 'GM01');

REM Table ITEM
        drop table ITEM;
        create table ITEM (
          ITEM_CODE      number(4)
            constraint PK_ITEM primary key
              using index tablespace DATA_INDEX
              pctfree 5,
          DESCRIIPTION   varchar2(50) default NULL,
          NORMAL_CHARGE number(7,2)
    )
        tablespace DATA;

Insert into ITEM values (2222, 'Syringe, 19 gauge', 7.54);
Insert into ITEM values (2233, '9 inch gauze', 2.21);
Insert into ITEM values (2244, 'Tylenol 800MG', 4.50);
Insert into ITEM values (2223, 'Morphine Drip, 0.2 liter', 284.59);
Insert into ITEM values (2255, 'Saline Soln, 1 liter', 25.00);
Insert into ITEM values (2243, 'Syringe, 8 gauge', 6.68);
Insert into ITEM values (2267, 'Bed Pan', 4.92);
Insert into ITEM values (2266, 'Surgical Prep Pack #2', 195.95);
Insert into ITEM values (2265, '4 inch gauze', 1.19);
Insert into ITEM values (2245, 'Surgical Prep Pack #8', 167.67);
Insert into ITEM values (2268, 'Bandaid, 3 inch', 0.76);
Insert into ITEM values (2242, '4 inch dressing', 4.56);
Insert into ITEM values (2224, 'Surgical Prep Pack #4', 222.21);

REM Table PHYSICIAN
        drop table PHYSICIAN;
        create table PHYSICIAN (
          PHY_ID         number(4)
            constraint PK_PHYSICIAN primary key
              using index tablespace DATA_INDEX
              pctfree 5,
          PHY_PHONE      char(8) default NULL,
          PHY_NAME       varchar2(50)
            constraint NN_PHY_NAME NOT NULL
    )
        tablespace DATA;

Insert into PHYSICIAN values (8880, '888-0001', 'Dr. Oprah Heart');
Insert into PHYSICIAN values (8887, '888-0007', 'Dr. Hawkeye Pierce');
Insert into PHYSICIAN values (8882, '888-0002', 'Dr. Jonas Salkman');
Insert into PHYSICIAN values (8884, '888-0004', 'Dr. Winifred Winfield');
Insert into PHYSICIAN values (8886, '888-0006', 'Dr. Trapper John');

REM Table PROCEDURES
        drop table PROCEDURES;
        create table PROCEDURES (
          PROCEDURE_NO       number(4)
            constraint PK_PROCEDURES primary key
              using index tablespace DATA_INDEX
              pctfree 5,
          PROC_DESCRIPTION varchar2(50)
    )
        tablespace DATA;

Insert into PROCEDURES values (3225, 'Appendectomy');
Insert into PROCEDURES values (3233, 'Lobotomy');
Insert into PROCEDURES values (3234, 'Thoracic Procedure');
Insert into PROCEDURES values (3232, 'Cervical Disk');
Insert into PROCEDURES values (3230, 'Hip Replacement');
Insert into PROCEDURES values (3231, 'Arthroscopic Procedure');
Insert into PROCEDURES values (3237, 'Ingrown Toenail');

REM Table TREATS
drop table TREATS;
create table TREATS (
    PHY_ID       number(4),
          PATIENT_NO   number(4),
    PROCEDURE_NO number(5),
    DATE_TREATED date,
          TREAT_RESULT varchar2(50) default NULL,
        constraint FK_TREATS_PATIENT foreign key (PATIENT_NO)
          references PATIENT
          on delete cascade,
        constraint FK_TREATS_PHYSICIAN foreign key (PHY_ID)
          references PHYSICIAN
          on delete cascade,
       constraint FK_TREATS_PROCEDURES foreign key (PROCEDURE_NO)
          references PROCEDURES
          on delete cascade,
        constraint PK_TREATS
          primary key (PHY_ID, PATIENT_NO, PROCEDURE_NO, DATE_TREATED)
          using index tablespace DATA_INDEX
          pctfree 5
   )
        tablespace DATA;

Insert into TREATS values (8887, 1117, 3232, '17-DEC-01','Repaired Disk OK');
Insert into TREATS values (8882, 1113, 3230, '18-DEC-01','Repaired Right Hip OK');
Insert into TREATS values (8887, 1113, 3232, '17-DEC-01','Repaired Disk OK');
Insert into TREATS values (8884, 1114, 3233, '15-DEC-01','Brain Partially Removed');
Insert into TREATS values (8886, 1116, 3234, '19-DEC-01','Removed Left Lung');
Insert into TREATS values (8880, 1111, 3237, '15-DEC-01','Removed toenail');
Insert into TREATS values (8886, 1115, 3230, '17-DEC-01','Repaired Left Hip OK');
Insert into TREATS values (8887, 1112, 3231, '18-DEC-01','Repaired Left Knee OK');
Insert into TREATS values (8887, 1112, 3231, '19-DEC-01','Repaired Right Knee OK');

REM Table BILLED
drop table BILLED;
create table BILLED (
    BILL_NO    number(5),
          PATIENT_NO number(4),
    ITEM_CODE number(5),
    CHARGE     number(7,2),
        constraint FK_BILLED_PATIENT foreign key (PATIENT_NO)
          references PATIENT
          on delete cascade,
        constraint FK_BILLED_ITEM foreign key (ITEM_CODE)
          references ITEM
          on delete cascade,
        constraint PK_BILLED
          primary key (BILL_NO)
          using index tablespace DATA_INDEX
          pctfree 5
   )
        tablespace DATA;

Insert into BILLED values (00001, 1117, 2222, 7.54);
Insert into BILLED values (00002, 1113, 2233, 2.21);
Insert into BILLED values (00003, 1117, 2255, 25.00);
Insert into BILLED values (00004, 1113, 2222, 7.75);
Insert into BILLED values (00005, 1115, 2245, 175.00);
Insert into BILLED values (00006, 1116, 2242, 4.56);
Insert into BILLED values (00007, 1112, 2224, 225.00);
Insert into BILLED values (00008, 1112, 2245, 167.67);
Insert into BILLED values (00009, 1116, 2243, 6.68);
Insert into BILLED values (00010, 1112, 2245, 167.67);
Insert into BILLED values (00011, 1112, 2224, 222.21);
Insert into BILLED values (00012, 1112, 2267, 4.92);
Insert into BILLED values (00013, 1117, 2245, 167.67);
Insert into BILLED values (00014, 1117, 2224, 222.21);
Insert into BILLED values (00015, 1117, 2267, 4.92);

REM End of Database Table and Data Insertion Code
REM Now create the public synonyms to allow easy access
REM by students to the tables.

drop public synonym BILLED;
create public synonym BILLED for DBOCK.BILLED;
drop public synonym ROOM;
create public synonym ROOM for DBOCK.ROOM;
drop public synonym PATIENT;
create public synonym PATIENT for DBOCK.PATIENT;
drop public synonym ITEM;
create public synonym ITEM for DBOCK.ITEM;
drop public synonym TREATS;
create public synonym TREATS for DBOCK.TREATS;
drop public synonym PHYSICIAN ;
create public synonym PHYSICIAN for DBOCK.PHYSICIAN;
drop public synonym PROCEDURES;
create public synonym PROCEDURES for DBOCK.PROCEDURES;

REM End of Script

END OF NOTES

BILLED
BILL_NO	NUMBER(5) - PRI KEY
PATIENT_NO	NUMBER(9)
ITEM_CODE	NUMBER(5)
CHARGE	NUMBER(7,2)

TREATS
PHY_ID	NUMBER(4) - PRI KEY
PATIENT_NO	NUMBER(4) - PRI KEY
PROCEDURE_NO	NUMBER(4) - PRI KEY
DATE_TREATED	DATE - PRI KEY
TREAT_RESULT	VARCHAR2(50)

ITEM
ITEM_CODE	NUMBER(4) - PRI KEY
DESCRIPTION	VARCHAR2(50)
NORMAL_CHARGE	NUMBER(7,2)

PHYSICIANS
PHY_ID	NUMBER(4) - PRI KEY
PHY_PHONE	CHAR(8)
PHY_NAME	VARCHAR2(50)

PATIENT
PATIENT_NO	NUMBER(4) - PRI KEY
DATE_LAST_TREATED	DATE
PAT_NAME	VARCHAR2(50)
ROOM_LOCATION	CHAR(4)

ROOM
ROOM_LOCATION	CHAR(4) - PRI KEY
ROOM_ACCOMODATION	CHAR(2)
ROOM_EXTENSION	NUMBER(4)

PROCEDURES
PROCEDURE_NO	NUMBER(4) - PRI KEY
PROC_DESCRIPTION	VARCHAR2(50)