SQL Introduction Chapter 7, sections 4.4 & 6.4. SQL Functions Aggregate functions. Aggregate Functions: MAX & MIN. Aggregate Functions

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1 SQL Introduction Chapter 7, sections 4.4 & 6.4 Objectives: to learn The basic commands and functions of SQL How to use SQL to query a database for useful information How to display the data so that it is easily readable. Outline Aggregate Functions Listing DISTINCT Values System Date Review SQLPlus Commands & formatting Queries with Compound conditions, computed values, & Special Operators Ordering the output 1 SQL Functions Aggregate functions The SQL Numeric Functions 2 Aggregate Functions Aggregate Functions: MAX & MIN COUNT function tallies number of non-null values of an attribute Takes one parameter: usually a column name MAX and MIN find highest (lowest) value in a table Compute MAX value in inner query Compare to each value returned by the query SUM computes total sum for any specified attribute AVG function format is similar to MIN and MAX 3 SELECT MAX(SAL) FROM EMP; SELECT MIN(SAL) FROM EMP; SELECT EMPNO, ENAME FROM EMP WHERE SAL = (SELECT MAX(SAL) FROM EMP); MAX(SAL) MIN(SAL)

2 Aggregate Functions: SUM Aggregate Functions: AVG SELECT SUM(COMM) FROM BONUS; SUM(COMM) SELECT SUM(SAL) FROM EMP; SUM(SAL) SELECT AVG(SAL) FROM EMP; AVG(SAL) SELECT EMPNO, ENAME, JOB FROM EMP WHERE SAL > (SELECT AVG(SAL) FROM EMP) ORDER BY SAL DESC; EMPNO ENAME JOB KING PRESIDENT 7902 FORD ANALYST 7788 SCOTT ANALYST 7566 JONES MANAGER 7698 BLAKE MANAGER 7782 CLARK MANAGER 6 Aggregate Functions: COUNT Listing Unique Values SELECT COUNT (JOB) FROM EMP; COUNT(JOB) SELECT COUNT (DISTINCT JOB) FROM EMP; COUNT(DISTINCTJOB) SELECT COUNT (DISTINCT JOB) FROM EMP WHERE DEPTNO = 20; DISTINCT (Unique) keyword produces list of only values that are different from one another It will produce 1 row per unique attribute. Useful where joining tables in a M:1 relationship and not listing the value multiple times RDBMS differences: Access places nulls at the top of the list Oracle places it at the bottom Placement of nulls does not affect list contents COUNT(DISTINCTJOB)

3 Distinct Keyword System Date Function Example: SELECT DISTINCT DEPTNO FROM EMP; Limits queries to: Entries having no duplicates DEPTNO Entries whose duplicates may be grouped SYSDATE function -retrieves the current date & time. SELECT SYSDATE FROM DUAL; SELECT ENAME FROM EMP WHERE HIREDATE <= SYSDATE; Eliminating the time from the date SELECT TRUNC(SYSDATE) FROM DUAL; Asking how many years employees have worked. SELECT (SYSDATE - HIREDATE)/365 FROM EMP; 9 10 Review Basic SQLPlus Interface Review Basic SQLPLUS Commands MENU System File: Open, Save, Spool Open will set your local directory path Editing Invoking the editor Temp file afied.buf Saving from the editor Options -> Environment Pagesize Linesize >RUN [/] Executes the sql statement in the buffer >LIST [l] Displays current statement in the buffer >DESCRIBE Displays attribute information for a table >EDIT [ed] invokes host operating system text editor >EXIT terminates session

4 Review Basic SQLPLUS Commands Scripting SQL from TEXT FILES >GET <filename> Retrieves SQL statement from a file and puts it into the active buffer. >SAVE <filename> Saves the active SQL statement in named file >START <filename> Allows execution of multiple SQL statements from a file >SPOOL <filename> off Saves session history in named file Basic SQLPLUS Formatting your Output TTITLE, BTITLE OFF ON COLUMN <options> Column Alias Select p_price*p_onhand Stock Worth from Product; FOR[MAT] format JUS[TIFY] L C R HEA[DING] text WRA[PPED] TRU[NCATED] WOR[D-WRAPPED] CLEAR <option> Clears specified option ( ttitle, columns, screen, sql, breaks) CS275 - Fall CS275 - Fall Basic SQLPLUS SQL LABS Commenting your Source REM single line comment /*.*/ multi-line, block comment Use Ttitleto put a report title on your output, use Rem to comment your source code scripts SQLPLUS Help:? Command Check the Website Resource page for more details Have COVER PAGE that lists the problem# and page. Turn in both SOURCE CODE (the.sqlfile) & EXECUTION (the spool file -.lst file) DO NOT Cut & Paste, i.e. Word processing in the.lst file, i.e. the Execution output! Put in REM s to mark Problem# sin the Source code Put in Ttitlesto mark Problem# sin the execution. When the problem shows you what the results must be, you ll need to reverse engineerthe problem from given output to appropriate SQL statement. CS275 - Fall CS275 - Fall

5 SELECT Queries Queries Compound Where Fine-tune SELECT command by adding restrictions to search criteria using: Conditional restrictions Compound Conditions /Logical operators Computed Columns/Arithmetic operators Special operators Searching data can involve multiple conditions Search criteria can be combined using Logical operators: AND, OR, and NOT Parentheses enforce precedence order Conditions in parentheses are always executed first Booleanalgebra: mathematical field dedicated to use of logical operators NOT negates result of conditional expression Queries Compound Where Examples Queries Compound Where Examples SELECT P_DESCRIPT,P_INDATE,P_PRICE,V_CODE WHERE V_CODE=21344 OR V_CODE=24288; SELECT P_DESCRIPT,P_INDATE,P_PRICE,V_CODE WHERE P_PRICE < 50 AND P_INDATE > TO_DATE( 07/15/96, mm/dd/yy );

6 Queries Compound Where Examples Queries Computed Columns SELECT P_DESCRIPT,P_INDATE,P_PRICE,V_CODE WHERE (P_PRICE < 50 AND P_INDATE > 15-JUL-96 ) OR V_CODE = 24288; Select p_descript, p_onhand, p_price, p_onhand*p_price from product; Computed Column with an Alias Arithmetic Operators: Rules of Precedence Select p_descript,p_onhand,p_price, p_onhand*p_price as totvalue from product; Mathematical expressions using multiple operators are performed in the following order: 1. Perform operations within parentheses 2. Perform power operations (uses a SQL function) 3. Perform multiplications and divisions 4. Perform additions and subtractions

7 QUERIES Special Operator BETWEEN BETWEEN: checks whether attribute value is within a range Examples SELECT * WHERE P_PRICE BETWEEN AND ; SELECT * FROM CUST WHERE BALANCE BETWEEN 500 AND 1000; QUERIES Special Operator IN IN: checks whether attribute value matches any value within a (sub)set of listed values Examples SELECT * WHERE V_CODE IN (21344, 24288); SELECT * FROM INVOICE WHERE CUS_CODE IN (10018,10011,10015); SELECT Query Keywords: ORDER BY SQL allows the use to specify the output order ORDER BY clause is useful when listing order is important Syntax: SELECT columnlist FROM tablelist [WHERE conditionlist] [ORDER BY columnlist[asc DESC]]; Ascending order by default Select ORDER BY Clause Ordering a Listing the ORDER BY clause SELECT P_CODE, P_DESCRIPT, P_INDATE,P_PRICE ORDER BY P_PRICE;

8 Select ORDER BY Clause SELECT P_CODE, P_DESCRIPT, P_INDATE, P_PRICE ORDER BY P_PRICE DESC; Select ORDER BY Clause SELECT EMP_LNAME, EMP_FNAME, EMP_INITIAL, EMP_AREACODE, EMP_PHONE FROM EMPLOYEE ORDER BY EMP_LNAME,EMP_FNAME,EMP_INITIAL; Selected PRODUCT Table Attributes: Ordered by (Descending) P_PRICE Select ORDER BY Clause SELECT P_DESCRIPT, V_CODE, P_INDATE,P_PRICE WHERE P_INDATE < 15-NOV-96 AND P_PRICE <= ORDER BY V_CODE DESC, P_PRICE DESC; 31 Summary The basic SELECT statement with Aggregate & sysdate functions Computed Columns with Aliases Using the SQLPlus environment Setting the Environment & Formatting the output. Creating and using script files The Where clause can use these types of conditions Conditional restrictions: =, >=,!=, <> <= Compound Conditions: using and & or Special operators: Between(data range) & In (list of items) The output display can be arranged ascending or descending by using the Order By clause. 32 8