java - 这一条sql哪里错了呀？

Question

SELECT a.*,b.custom_name FROM zqwl_receipt a , zqwl_custom b LEFT JOIN b WHERE a.id= b.id

Answer 1

left join的用法一般是先查詢主表再join其他表的，例如

select a.*, b.custom_name from zqwl_receipt a
left join zqwl_custom b on a.id = b.id

如果你希望a、b兩個表結合查詢的結果再做關聯查找的話，或許可以用子查詢的方式

select * from (
  select a.*, b.custom_name from zqwl_receipt a, zqwl_custom b where a.id = b.id
) t
left join zqwl_custom t2 on t2.id = t.id

但是如果寫出這樣的語句來，最好要要思考a, b兩個表的設計問題，
或者這完全就是沒有必要的

Answer 2

從 xxx LEFT JOIN xxx 選擇 zqwl_receipt.*,zqwl_custom.custom_name

Answer 3

從a左加入b on a.id=b.id

Answer 4

你的FROM 去哪裡了

Answer 5

沒有 from 表
沒有 on 來篩選這兩個表的關係。

SELECT zqwl_receipt.*,zqwl_custom.custom_name from zqwl_receipt LEFT JOIN zqwl_custom on zqwl_custom.欄位= zqwl_receiptwl_custom on zqwl_custom.欄位= zqwl_receiptwl_custom

on zqwl_custom.字段= zqwl_receipt.wl_custom 🎜on zqwl_custom.欄位= zqwl_receipt.T.

Answer 6

基本語法錯誤