SELECT select1,select3 FROM table1 WHERE where1 UNION SELECT select2 FROM table2 WHERE where2 order by select3.id desc limit limit1 提示我unknow table "select3" 还有就是limit子句是不是这样用也不行啊?
当然了UNION 要保证字段数量绝对相等 类型要兼容
若select3为字符型则 SELECT select1,select3 FROM table1 WHERE where1 UNION SELECT select2,'' FROM table2 WHERE where2若select3为数值型则 SELECT select1,select3 FROM table1 WHERE where1 UNION SELECT select2,0 FROM table2 WHERE where2每一个select子句都可以有limit 但请注意:最后一个limit将对全部查询结果起作用
还有个问题! SELECT select11,select12,select13,select14 FROM table1 WHERE where1 UNION SELECT select21,0,'',0,'' //select11,select13为数值型则 select12,select14为字符型则 FROM table2 WHERE where2 在网页select12,select13,select14字段显示出来后要么没有,要么只有一部分!是为什么啊?
UNION
SELECT select2 FROM table2 WHERE where2
order by select3.id desc
limit limit1
提示我unknow table "select3"
还有就是limit子句是不是这样用也不行啊?
类型要兼容
SELECT select1,select3 FROM table1 WHERE where1
UNION
SELECT select2,'' FROM table2 WHERE where2若select3为数值型则
SELECT select1,select3 FROM table1 WHERE where1
UNION
SELECT select2,0 FROM table2 WHERE where2每一个select子句都可以有limit
但请注意:最后一个limit将对全部查询结果起作用
SELECT select11,select12,select13,select14
FROM table1 WHERE where1
UNION
SELECT select21,0,'',0,''
//select11,select13为数值型则 select12,select14为字符型则
FROM table2 WHERE where2
在网页select12,select13,select14字段显示出来后要么没有,要么只有一部分!是为什么啊?