MySQL Classic SQL collection

1. SQL data storage by condition

普通的 INSERT INTO 插入：

INSERT INTO card(cardno, cardnum) VALUES(‘1111‘, ‘100‘);INSERT INTO card(cardno, cardnum) VALUES(‘2222‘, ‘200‘);

Inserting a condition into SQL

insert  INTO  Card (Cardno, Cardnum) select   ' 111 ' ,  ' " from  DUAL where  not  exists  (select  cardno from  Card where  Cardno =  ' 111 ' );  INSERT  into card (Cardno, cardnum) SELECT ' 222 ', '  + ' from DUAL where  not EXISTS(SELECT cardno  from card WHERE Cardno = ' 222 ');

2. Condition control

IF 语句CASE 语句IF 语句根据条件执行一系列语句，有三种形式：IF-THEN、IF-THEN-ELSE 和 IF-THEN-ELSIF

DECLARE  x VARCHAR2(10);BEGIN  x:=‘&x‘;  IF LOWER(x)=‘yTHEN    DBMS_OUTPUT.PUT_LINE(‘Yes!‘);  ELSIF LOWER(x)=‘nTHEN    DBMS_OUTPUT.PUT_LINE(‘No!‘);  ELSE    DBMS_OUTPUT.PUT_LINE(‘Error‘);  ENDIF;END;

The case statement is used to compare multiple values against a single variable or an expression
Calculates the value of a selector before executing a case statement

begin   Case  ' &grade ' when  ' A ' then  dbms_ OUTPUT.      Put_Line (' excellent '); when  ' B ' then  dbms_output.      Put_Line (excellent '); when  ' C ' then  dbms_output.      Put_Line (' good '); when  ' D ' then  dbms_output.      Put_Line (' General '); when  ' F ' then  dbms_output.      Put_Line (' poor '); else  Dbms_output.    Put_Line (' No such result '); end  case ; end ;  

3. Loop control for repeating a series of statements
Loop control statements include:
LOOP, exit, and exit when
Three types of loop control:
Loop-Unconditional Loop
While-looping by condition
For-loop fixed number of times

LOOP   sequence_of_statementsENDLOOP;WHILELOOP   sequence_of_statementsENDLOOP;FORIN [REVERSE] value1..value2LOOP   sequence_of_statementsENDLOOP;

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

MySQL Classic SQL collection