Chapter 03-Using Single-Row Functions to Customize Output(01)

Objectives

After completing this lesson,you should be able to do the following:

Describe various types of functions available in SQL.

Use character,number,and date functions in SELECT statements.

Lesson Agenda

Single-row SQL functions

Character functions

Number functions

Working with dates

Date functions

/* 函数是一定有返回值的，过程可以没有返回值. */

SQL Functions

Two Types of SQL 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 [(arg1,arg2,...)]

Character Functions

Case-Conversion Functions

These functioins convert case for character strings:

Function	Result
LOWER('SQL Course')	sql course
UPPER('SQL Course')	SQL COURSE
INITCAP('SQL Course')	Sql Course

Demo-01:

SQL> select LOWER('SQL COURSE') FROM DUAL;

LOWER('SQL
----------
sql course

SQL> SELECT UPPER('Sql Course') FROM DUAL;

UPPER('SQL
----------
SQL COURSE

SQL> SELECT INITCAP('SQL Course') FROM DUAL;

INITCAP('S
----------
Sql Course

Demo-02:

SQL> SELECT employee_id,last_name,department_id FROM employees WHERE last_name = 'higgins';

no rows selected

SQL> SELECT employee_id,last_name,department_id FROM employees WHERE LOWER(last_name) = 'higgins';

EMPLOYEE_ID LAST_NAME                 DEPARTMENT_ID
----------- ------------------------- -------------
205 Higgins                             110

Character-Manipulation Functions

These functions manipulate character strings:

Function	Result
CONCAT('Hello','World')	HelloWorld
SUBSTR('HelloWorld',1,5)	Hello
LENGTH('HelloWorld')	10
INSTR('HelloWorld','W')	6
LPAD(salary,10,"*")	*****24000
RPAD(salary,10,'*')	24000*****
REPLACE('Jack and JUE','J','BL')	BLACK and BLUE
TRIM('H' FROM 'HelloWorld')	ellowWorld

Demo-01:

SQL> SELECT CONCAT('Hello ','World') FROM DUAL;

CONCAT('HEL
-----------
Hello World

SQL> SELECT SUBSTR('HelloWorld',1,5) FROM DUAL;

SUBST
-----
Hello

SQL> SELECT LENGTH('HelloWorld') FROM DUAL;

LENGTH('HELLOWORLD')
--------------------
10

SQL> SELECT INSTR('HelloWorld','W') FROM DUAL;

INSTR('HELLOWORLD','W')
-----------------------
6

SQL> SELECT LPAD(salary,10,'*') FROM employees where employee_id=100;

LPAD(SALARY,10,'*')
----------------------------------------
*****24000

SQL> SELECT RPAD(salary,10,'*') FROM employees where employee_id=100;

RPAD(SALARY,10,'*')
----------------------------------------
24000*****

SQL> SELECT REPLACE('JACK and JUE','J','BL') FROM DUAL;

REPLACE('JACKA
--------------
BLACK and BLUE

SQL> SELECT TRIM('H' FROM 'HelloWorld') FROM DUAL;

TRIM('H'F
---------
elloWorld

Demo-02 :

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';

EMPLOYEE_ID NAME                 JOB_ID     LENGTH(LAST_NAME) Contains 'a'?
----------- -------------------- ---------- ----------------- -------------
202 arcerzhangFay        MK_REP                     3             2
203 SusanMavris          HR_REP                     6             2
204 HermannBaer          PR_REP                     4             2
150 PeterTucker          SA_REP                     6             0
151 DavidBernstein       SA_REP                     9             0
152 PeterHall            SA_REP                     4             2
153 ChristopherOlsen     SA_REP                     5             0
154 NanetteCambrault     SA_REP                     9             2
155 OliverTuvault        SA_REP                     7             4
156 JanetteKing          SA_REP                     4             0
157 PatrickSully         SA_REP                     5             0

EMPLOYEE_ID NAME                 JOB_ID     LENGTH(LAST_NAME) Contains 'a'?
----------- -------------------- ---------- ----------------- -------------
158 AllanMcEwen          SA_REP                     6             0
159 LindseySmith         SA_REP                     5             0
160 LouiseDoran          SA_REP                     5             4
161 SarathSewall         SA_REP                     6             4
162 ClaraVishney         SA_REP                     7             0
163 DanielleGreene       SA_REP                     6             0
164 MatteaMarvins        SA_REP                     7             2
165 DavidLee             SA_REP                     3             0
166 SundarAnde           SA_REP                     4             0
167 AmitBanda            SA_REP                     5             2
168 LisaOzer             SA_REP                     4             0

EMPLOYEE_ID NAME                 JOB_ID     LENGTH(LAST_NAME) Contains 'a'?
----------- -------------------- ---------- ----------------- -------------
169 HarrisonBloom        SA_REP                     5             0
170 TaylerFox            SA_REP                     3             0
171 WilliamSmith         SA_REP                     5             0
172 ElizabethBates       SA_REP                     5             2
173 SunditaKumar         SA_REP                     5             4
174 EllenAbel            SA_REP                     4             0
175 AlyssaHutton         SA_REP                     6             0
176 JonathonTaylor       SA_REP                     6             2
177 JackLivingston       SA_REP                    10             0
178 KimberelyGrant       SA_REP                     5             3
179 CharlesJohnson       SA_REP                     7             0

33 rows selected.