select * from table
从表table中查询所有数据
select * from table where "列名" = "?"
从表table中查询列名等于？的数据
update table set "列名1" = "?1" where "列名2" = "?2"
将表table中列名2的等于?2时将列名1的数据改为?1
insert into table values(????)
插入数据
delete from table where "列名" = "?"
将表中列名等于?的数据删除
select concat(colum1,colum2) as name from table
将table中colum1,colum2合并为name并打印
train(colum)
去除colum数据的空格
order by colum1
根据colum1进行升序排序,可有多个参数
order by column desc
根据colum1进行降序排序
select * from table limit num
输出num条数据
select * from table limit num1,num2
从num1开始输出num2条数据，不包num1;
select * from table1 as a,table2 as b where a.colum1 = b.cloum2
关联打印，将表a表b中相关的数据打印出来
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