在table 表的 id 字段之後,新增一個字段,設置對應的類型,長度,是否爲null,默認值,註釋
ALTERTABLE test ADDCOLUMN create_by VARCHAR(10)NOTNULLDEFAULT'system'COMMENT'創建者'AFTER`id`;
修改一個字段爲日期類型並設置默認爲當前日期與備註
ALTERTABLE test MODIFY create_date datetime NOTNULLDEFAULTNOW()COMMENT'更新日期';
修改一個字段的名稱,此時要重新指定該字段的類型
ALTERTABLE test CHANGE user_id create_by VARCHAR(10)NOTNULLDEFAULT'system'COMMENT'創建者';
刪除table表的 value字段
ALTERTABLE test DROPCOLUMN user_id;
刪除相領重複數據,保留一條
DELETE t2 FROM test t1,test t2 WHERE t1.aaa=t2.aaa AND t1.bbb=t2.bbb AND t1.ccc = t2.ccc AND t1.id<t2.id;
查詢相領重複數據,保留一條
SELECTDISTINCT t2.*FROM test t1
INNERJOIN test t2 ON t1.aaa=t2.aaa AND t1.bbb=t2.bbb AND t1.ccc = t2.ccc
WHERE t1.id<t2.id;
批量新增100個用戶->通過存儲過程
drop procedure IFEXISTS pre;
delimiter $$
create procedure pre()
begin
declare i int;set i=1;while i<101do
insert into sys_user(username,password)value(CONCAT('admin',i),'$2a$10$yRje.GJNSDbnDw4j3XtEReqnVAAjjR.gtoNTA7YF/EbELikgKZETe');set i=i+1;
end while;
end
$$
call pre();