MySQL数据库常用操作技巧总结

use information_schema;
select  from columns where column_name='字段名';

SELECT SQL_CALC_FOUND_ROWS  FROM TABLE WHERE 1=1;

SET @RowCount=found_rows();

/错误代码/
SET @RetCode='1';
/错误提示/
SET @RetVal='1';
/返回记录行数/
SET @RowCount='0';
/页码/
SET @PageCount='0';
/每页显示数/
SET @CurrentItem=0;
/每页显示数/
SET @PageSize=arg_page_size;
/页码/
SET @PageCurrent=arg_page_current;
SET @SqlExe='select  from table where 1=1';
入参arg_page_size int,arg_page_current int
IF(@PageCurrent IS NOT NULL && @PageSize IS NOT NULL) THEN
SET @CurrentItem = (@PageCurrent-1)@PageSize;
SET @SqlExe=CONCAT(@SqlExe,'LIMIT ', @PageSize,' OFFSET ', @CurrentItem);
ELSE
SET @SqlExe=CONCAT(@SqlExe,' ');
END IF;
prepare stmt from @SqlExe;
execute stmt;
deallocate prepare stmt;
IF(@RowCount IS NOT NULL && @RowCount != 0) THEN
IF(@PageSize is null)then
SET @PageSize= @RowCount;
END IF;
SET @PageCount = ceiling(@RowCount/@PageSize);
ELSE
SET @RowCount = 0;
SET @PageCount = 1;
END IF;

select left(content,200)as abstract from my_content_t

select right(content,200)as abstract from my_content_t

select substring(content,5)as abstract from my_content_t
select substring(content,5,200)as abstract from my_content_t

select substring_index("blog.csdn."，"."，2)as abstract from my_content_t

blog.csdn

mysql>select lower('DDD');
结果ddd
mysql> select upper('ddd');
结果DDD
mysql> select lcase('DDD');
结果ddd
mysql> select ucase('ddd');
结果DDD

declare _LastWeekStartTime date; -- 上周开始时间
declare _LastWeekEndTime date; -- 上周结束时间

set @A = date_add(curdate(), interval -1 day);

set @B = subdate( @A,date_format(@A,'%w')-1);

set @C = date_add(@B, interval -2 day);
set _LastWeekStartTime = ( subdate( @C,date_format( @C,'%w')-1));
set _LastWeekEndTime = ( date_add(subdate( @C,date_format( @C,'%w')-1), interval 6 day));

SET @nowdate=(select DAYOFWEEK(NOW()));
SET @NowD=case @nowdate
when 1 then '星期日'
when 2 then '星期一'
when 3 then '星期二'
when 4 then '星期三'
when 5 then '星期四'
when 6 then '星期五'
when 7 then '星期六'
end;

if (DATE_FORMAT(CURDATE(),'%w')=0) then
SET @curmon=(SELECT SUBDATE(CURDATE(),DATE_FORMAT(CURDATE(),'%w')+6));
SET @cursun=(SELECT SUBDATE(CURDATE(),DATE_FORMAT(CURDATE(),'%w')));
else

SET @curmon=(SELECT SUBDATE(CURDATE(),DATE_FORMAT(CURDATE(),'%w')-1));

SET @cursun=(SELECT SUBDATE(CURDATE(),DATE_FORMAT(CURDATE(),'%w')-7));

CREATE TABLE test (
id INT PRIMARY KEY not null auto_increment,
val nvarchar (50) NOT NULL
);
INSERT INTO test(val) VALUES ('0');
INSERT INTO test(val) VALUES ('1');
INSERT INTO test(val) VALUES ('2');
INSERT INTO test(val) VALUES ('3');
SELECT  from test;
-- 根据 id为 2 0 1 3的优先级自定义排序
SELECT  FROM test ORDER BY instr('2013',id);
-- 原理样例
SET @ORDBYD='2013';
SELECT '2',instr(@ORDBYD,'2') as `INDEX`
union
SELECT '0',instr(@ORDBYD,'0') as `INDEX`
union
SELECT '1',instr(@ORDBYD,'1') as `INDEX`
union
SELECT '3',instr(@ORDBYD,'3') as `INDEX`;

SELECT instr('syranmo','s') FROM dual; -- 返回 1
SELECT instr('syranmo','ra') FROM dual; -- 返回 3
SELECT instr('syran mo','at',1,2) FROM dual; -- 返回 0