Substitution Variables 3 Copyright 2007 Oracle All rights

Substitution Variables So far, all the SQL statements were executed with predetermined columns, conditions and their values. Suppose that you want a query that lists the employees with various jobs. You can edit the WHERE clause to provide a different value each time you run the command, but there is also an easier way. 3 -2 Copyright © 2007, Oracle. All rights reserved.

Substitution Variables By using a substitution variable in place of the exact values in the WHERE clause, you can run the same query for different values. You can create reports that prompt users to supply their own values to restrict the range of data returned, by using substitution variables. 3 -3 Copyright © 2007, Oracle. All rights reserved.

Substitution Variables(continued) • Use substitution variables to: – Temporarily store values with single-ampersand (&) and double-ampersand (&&) substitution • Use substitution variables to supplement the following: – – – 3 -4 WHERE conditions ORDER BY clauses Column expressions Table names Entire SELECT statements Copyright © 2007, Oracle. All rights reserved.

3 -5 Copyright © 2007, Oracle. All rights reserved.

Substitution Variables(continued) You can use single-ampersand (&) substitution variables to temporarily store values. You can also predefine variables by using the DEFINE command. DEFINE creates and assigns a value to a variable. DEFINE var_name = value; 3 -6 Copyright © 2007, Oracle. All rights reserved.

Use an ampersand (&) to identify each variable in your SQL statement. However, you do not need to define the value of each variable. Notation Description &user_variable Indicates a variable in a SQL statement; if the variable does not exist, SQL*Plus or SQL Developer prompts the user for a value (the new variable is discarded after it is used. ) With the single ampersand, the user is prompted every time the command is executed if the variable does not exist. 3 -7 Copyright © 2007, Oracle. All rights reserved.

Using the Single-Ampersand Substitution Variables 3 -8 Copyright © 2007, Oracle. All rights reserved.

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Using the Double. Ampersand Substitution Variable You can use the double-ampersand (&&) substitution variable to reuse the variable value without prompting the user each time. The user sees the prompt for the value only once. If you run the query again, you will not be prompted for the value of the variable. SQL Developer stores the value that is supplied by using the DEFINE command; it uses it again whenever you reference the variable name. After a user variable is in place, you need to use the UNDEFINE command to delete it: UNDEFINE column_name 3 - 12 Copyright © 2007, Oracle. All rights reserved.

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Using Single-Row Functions to Customize Output 3 - 15 Copyright © 2007, Oracle. All

SQL Functions Input Output Function performs action arg 1 arg 2 Result value arg

Two Types of SQL Functions 3 - 17 Single-row functions Multiple-row functions Return one

Single-Row Functions Single-row functions: • Manipulate data items • Accept arguments and return one value • Act on each row that is returned • Return one result per row • May modify the data type • Can be nested • Accept arguments that can be a column or an expression function_name [(arg 1, arg 2, . . . )] 3 - 18 Copyright © 2007, Oracle. All rights reserved.

Single-Row Functions Character Single-row functions General Conversion 3 - 19 Number Date Copyright ©

Character Functions Character functions 3 - 20 Case-conversion functions Character-manipulation functions LOWER UPPER INITCAP CONCAT SUBSTR LENGTH INSTR LPAD | RPAD TRIM REPLACE Copyright © 2007, Oracle. All rights reserved.

Case-Conversion Functions These functions convert the case for character strings: 3 - 21 Function Result LOWER('SQL Course') sql course UPPER('SQL Course') SQL COURSE INITCAP('SQL Course') Sql Course Copyright © 2007, Oracle. All rights reserved.

Using Case-Conversion Functions Display the employee number, name, and department number for employee Higgins: SELECT employee_id, last_name, department_id FROM employees WHERE last_name = 'higgins'; SELECT employee_id, last_name, department_id FROM employees WHERE LOWER(last_name) = 'higgins'; 3 - 22 Copyright © 2007, Oracle. All rights reserved.

Character-Manipulation Functions These functions manipulate character strings: 3 - 23 Function Result CONCAT('Hello', 'World') Hello. World SUBSTR('Hello. World', 1, 5) Hello LENGTH('Hello. World') 10 INSTR('Hello. World', 'W') 6 LPAD(salary, 10, '*') *****24000 RPAD(salary, 10, '*') 24000***** REPLACE ('JACK and JUE', 'J', 'BL') BLACK and BLUE TRIM('H' FROM 'Hello. World') ello. World Copyright © 2007, Oracle. All rights reserved.

Using the Character-Manipulation Functions 1 SELECT employee_id, CONCAT(first_name, last_name) NAME, job_id, LENGTH (last_name), INSTR(last_name, 'a') "Contains 'a'? " FROM employees WHERE SUBSTR(job_id, 4) = 'REP'; 1 3 - 24 2 Copyright © 2007, Oracle. All rights reserved. 3 2 3

Number Functions • ROUND: Rounds value to a specified decimal • TRUNC: Truncates value to a specified decimal • MOD: Returns remainder of division 3 - 25 Function Result ROUND(45. 926, 2) 45. 93 TRUNC(45. 926, 2) 45. 92 MOD(1600, 300) 100 Copyright © 2007, Oracle. All rights reserved.

Using the ROUND Function 1 2 SELECT ROUND(45. 923, 2), ROUND(45. 923, 0), ROUND(45. 923, -1) FROM DUAL; 1 2 3 3 DUAL is a dummy table that you can use to view results from functions and calculations. 3 - 26 Copyright © 2007, Oracle. All rights reserved.

Using the TRUNC Function 1 2 SELECT TRUNC(45. 923, 2), TRUNC(45. 923, -1) FROM

Using the MOD Function For all employees with the job title of Sales Representative, calculate the remainder of the salary after it is divided by 5, 000. SELECT last_name, salary, MOD(salary, 5000) FROM employees WHERE job_id = 'SA_REP'; 3 - 28 Copyright © 2007, Oracle. All rights reserved.

Working with Dates • The Oracle database stores dates in an internal numeric format: century, year, month, day, hours, minutes, and seconds. • The default date display format is DD-MON-RR. – Enables you to store 21 st-century dates in the 20 th century by specifying only the last two digits of the year – Enables you to store 20 th-century dates in the 21 st century in the same way SELECT last_name, hire_date FROM employees WHERE hire_date < '01 -FEB-88'; 3 - 29 Copyright © 2007, Oracle. All rights reserved.

RR Date Format Current Year 1995 2001 Specified Date 27 -OCT-95 27 -OCT-17 27 -OCT-95 RR Format 1995 2017 1995 YY Format 1995 1917 2095 If the specified two-digit year is: If two digits of the current year are: 3 - 30 0– 49 50– 99 0– 49 The return date is in the current century 50– 99 The return date is in the century after the current one The return date is in the century before the current one The return date is in the current century Copyright © 2007, Oracle. All rights reserved.

Using the SYSDATE Function SYSDATE is a function that returns: • Date • Time

Arithmetic with Dates • Add or subtract a number to or from a date for a resultant date value. • Subtract two dates to find the number of days between those dates. • Add hours to a date by dividing the number of hours by 24. 3 - 32 Copyright © 2007, Oracle. All rights reserved.

Using Arithmetic Operators with Dates SELECT last_name, (SYSDATE-hire_date)/7 AS WEEKS FROM employees WHERE department_id

Date-Manipulation Functions 3 - 34 Function Result MONTHS_BETWEEN Number of months between two dates ADD_MONTHS Add calendar months to date NEXT_DAY Next day of the date specified LAST_DAY Last day of the month ROUND Round date TRUNC Truncate date Copyright © 2007, Oracle. All rights reserved.

Using Date Functions 3 - 35 Function Result MONTHS_BETWEEN ('01 -SEP-95', '11 -JAN-94') 19. 6774194 ADD_MONTHS (‘ 31 -JAN-96', 1) ‘ 29 -FEB-96' NEXT_DAY ('01 -SEP-95', 'FRIDAY') '08 -SEP-95' LAST_DAY ('01 -FEB-95') '28 -FEB-95' Copyright © 2007, Oracle. All rights reserved.

Using ROUND and TRUNC Functions with Dates Assume SYSDATE = '25 -JUL-03': 3 - 36 Function Result ROUND(SYSDATE, 'MONTH') 01 -AUG-03 ROUND(SYSDATE , 'YEAR') 01 -JAN-04 TRUNC(SYSDATE , 'MONTH') 01 -JUL-03 TRUNC(SYSDATE , 'YEAR') 01 -JAN-03 Copyright © 2007, Oracle. All rights reserved.

Conversion Functions Data type conversion Implicit data type conversion 4 - 37 Explicit data

Implicit Data Type Conversion In expressions, the Oracle server can automatically convert the following: 4 - 38 From To VARCHAR 2 or CHAR NUMBER VARCHAR 2 or CHAR DATE Copyright © 2007, Oracle. All rights reserved.

Implicit Data Type Conversion • Oracle server can automatically perform data type conversion in an expression. • For example, the expression hire_date > '01 -JAN-90' results in the implicit conversion from the string '01 -JAN-90' to a date. • Therefore, a VARCHAR 2 or CHAR value can be implicitly converted to a number or date data type in an expression. 4 - 39 Copyright © 2007, Oracle. All rights reserved.

Implicit Data Type Conversion For expression evaluation, the Oracle server can automatically convert the following: 4 - 40 From To NUMBER VARCHAR 2 or CHAR DATE VARCHAR 2 or CHAR Copyright © 2007, Oracle. All rights reserved.

Explicit Data Type Conversion TO_NUMBER CHARACTER TO_CHAR 4 - 41 TO_DATE TO_CHAR Copyright ©

Using the TO_CHAR Function with Dates TO_CHAR(date, 'format_model') The format model: • Must be enclosed with single quotation marks • Is case-sensitive • Can include any valid date format element • Has an fm element to remove padded blanks or suppress leading zeros • Is separated from the date value by a comma 4 - 42 Copyright © 2007, Oracle. All rights reserved.

Elements of the Date Format Model 4 - 43 Element Result YYYY Full year in numbers YEAR Year spelled out (in English) MM Two-digit value for the month MONTH Full name of the month MON Three-letter abbreviation of the month DY Three-letter abbreviation of the day of the week DAY Full name of the day of the week DD Numeric day of the month Copyright © 2007, Oracle. All rights reserved.

Elements of the Date Format Model • Time elements format the time portion of the date: HH 24: MI: SS AM 15: 45: 32 PM • Add character strings by enclosing them with double quotation marks: DD "of" MONTH 12 of OCTOBER • Number suffixes spell out numbers: ddspth 4 - 44 fourteenth Copyright © 2007, Oracle. All rights reserved.

Using the TO_CHAR Function with Dates SELECT last_name, TO_CHAR(hire_date, 'fm. DD Month YYYY') AS

Using the TO_CHAR Function with Numbers TO_CHAR(number, 'format_model') These are some of the format elements that you can use with the TO_CHAR function to display a number value as a character: 4 - 46 Element 9 Result 0 Forces a zero to be displayed $ Places a floating dollar sign L Uses the floating local currency symbol . Prints a decimal point , Prints a comma as a thousands indicator Represents a number Copyright © 2007, Oracle. All rights reserved.

Using the TO_CHAR Function with Numbers SELECT TO_CHAR(salary, '$99, 999. 00') SALARY FROM employees

Using the TO_NUMBER and TO_DATE Functions • Convert a character string to a number format using the TO_NUMBER function: TO_NUMBER(char[, 'format_model']) • Convert a character string to a date format using the TO_DATE function: TO_DATE(char[, 'format_model']) 4 - 48 Copyright © 2007, Oracle. All rights reserved.

Using the TO_CHAR and TO_DATE Function with RR Date Format To find employees hired before 1990, use the RR date format, which produces the same results whether the command is run in 1999 or now: SELECT last_name, TO_CHAR(hire_date, 'DD-Mon-YYYY') FROM employees WHERE hire_date < TO_DATE('01 -Jan-90', 'DD-Mon-RR'); 4 - 49 Copyright © 2007, Oracle. All rights reserved.

Nesting Functions • Single-row functions can be nested to any level. • Nested functions are evaluated from the deepest level to the least deep level. F 3(F 2(F 1(col, arg 1), arg 2), arg 3) Step 1 = Result 1 Step 2 = Result 2 Step 3 = Result 3 4 - 50 Copyright © 2007, Oracle. All rights reserved.

Nesting Functions SELECT last_name, UPPER(CONCAT(SUBSTR (LAST_NAME, 1, 8), '_US')) FROM employees WHERE department_id =

General Functions The following functions work with any data type and pertain to using nulls: • NVL (expr 1, expr 2) • NVL 2 (expr 1, expr 2, expr 3) • NULLIF (expr 1, expr 2) • COALESCE (expr 1, expr 2, . . . , exprn) 4 - 52 Copyright © 2007, Oracle. All rights reserved.

NVL Function Converts a null value to an actual value: • Data types that can be used are date, character, and number. • Data types must match: – NVL(commission_pct, 0) – NVL(hire_date, '01 -JAN-97') – NVL(job_id, 'No Job Yet') 4 - 53 Copyright © 2007, Oracle. All rights reserved.

Using the NVL Function 1 SELECT last_name, salary, NVL(commission_pct, 0), (salary*12) + (salary*12*NVL(commission_pct, 0)) AN_SAL FROM employees; … 4 - 54 1 2 Copyright © 2007, Oracle. All rights reserved. 2

Using the NVL 2 Function SELECT last_name, salary, commission_pct, 1 NVL 2(commission_pct, 2 'SAL+COMM', 'SAL') income FROM employees WHERE department_id IN (50, 80); 1 4 - 55 Copyright © 2007, Oracle. All rights reserved. 2

Using the NULLIF Function 1 SELECT first_name, LENGTH(first_name) "expr 1", 2 last_name, LENGTH(last_name) "expr 2", NULLIF(LENGTH(first_name), LENGTH(last_name)) result FROM employees; … 1 4 - 56 2 Copyright © 2007, Oracle. All rights reserved. 3 3

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4 - 58 Copyright © 2007, Oracle. All rights reserved.

Homework : 1. Write a query to display the system date. Label the column Date. 2. Display the employee number, last name, salary, and salary increased by 15. 5%(expressed as a whole number)for each employee. Label the column New Salary. 3. Write a query that displays the last name (with the first letter in uppercase and all the other letters in lowercase)and the length of the last name for all employees whose name starts with the letters the user prompts to enter, make the case of the entered letter doesn’t affect. Give each column an appropriate label. Sort the results by the employees’ last names. 4 - 59 Copyright © 2007, Oracle. All rights reserved.

4. Create a query to display the last name and the number of weeks employed for all employees in department 90. Label the number of weeks column as TENURE. Truncate the number of weeks value to 0 decimal places. Show the records in descending order of the employee’s tenure. 5. Create a query that displays the employees’ last names and commission amounts. If an employee does not earn commission, show “No Commission. ” Label the column as COMM. 4 - 60 Copyright © 2007, Oracle. All rights reserved.