sql编程中流程控制 IF ……THEN……ELSEIF……THEN………END IF

写mysql存储过程应注意的几点：

1、声明变量（declare）时要注意字符集，用变量存储表字段时，表字段与变量的字符编码要一致。

2、mysql的字符合并不能用‘+’号，必须用concat函数。

3、每个游标必须使用不同的declare continue handler for not found set done=1来控制游标的结束。

BEGIN

declare rt VARCHAR(100) CHARACTER SET gbk DEFAULT NULL;

declare done tinyint(1) default 0;

DECLARE ttname VARCHAR(60) CHARACTER SET gbk DEFAULT NULL;

DECLARE tsqltxt VARCHAR(512) CHARACTER SET gbk DEFAULT NULL;

DECLARE tremarks VARCHAR(60) CHARACTER SET gbk DEFAULT NULL;

DECLARE tfield VARCHAR(60) CHARACTER SET gbk DEFAULT NULL;

DECLARE curtable CURSOR FOR

SELECT distinct TABLE_name

FROM information_schema.TABLEs where TRIM(TABLE_COMMENT)<>'' and TRIM(TABLE_COMMENT)<>'VIEW'  order by TABLE_name;

declare continue handler for not found set done=1;

set NAMES 'utf8';

drop table if EXISTS GetTableSQL;

CREATE TABLE `gettablesql` (

`tbname` varchar(60) CHARACTER SET gbk DEFAULT NULL,

`sqltxt` varchar(4096) CHARACTER SET gbk DEFAULT NULL,

`tabletitle` varchar(51) CHARACTER SET gbk DEFAULT NULL

) ENGINE=InnoDB;

open curtable;

tableloop:

LOOP

set tsqltxt='select';

FETCH curtable

INTO ttname;

IF done = 1 THEN

LEAVE tableloop;

END IF;

-- select ttname;

BEGIN

declare done1 tinyint(1) default 0;

DECLARE curfield CURSOR FOR

SELECT  COLUMN_NAME,COLUMN_COMMENT

FROM information_schema.COLUMNS  where upper(TABLE_name)=upper(ttname) and (COLUMN_COMMENT<>'') ;

declare continue handler for not found set done1=1;

OPEN curfield;

fieldloop:

LOOP

FETCH curfield

INTO tfield,tremarks;

IF done1 = 1 THEN

LEAVE fieldloop;

END IF;

if tsqltxt='select' THEN

set tsqltxt=CONCAT(tsqltxt,' ',tfield,' ','''',tremarks,'''');

ELSE

set tsqltxt=CONCAT(tsqltxt,',',tfield,' ','''',tremarks,'''');

END IF;

END LOOP fieldloop;

close curfield;

set tsqltxt=concat(tsqltxt,' from ',ttname);

insert into GetTableSQL values(ttname,tsqltxt,'');

END;

END LOOP tableloop;

close curtable;

update GetTableSQL as G set tabletitle=(select TABLE_COMMENT from information_schema.TABLEs  s

where (trim(s.TABLE_COMMENT)<>'') and g.tbname=s.table_name );

select cast(count(*) as char) into rt from GetTableSQL;

set rt=concat('成功更新',rt,'个表的表名注释和字段注释到字典库GetTableSQL中！');

SELECT rt;

END