Mysql選擇多個表，但內部連接在一個表上

Question

是否可以選擇多個表並在其中一個表上進行內部連接？例如

SELECT * 
FROM table1 AS t1, table2 AS t2, table3 AS t3 
INNER JOIN table4 AS t4 ON t1.row3 = t4.row3 
INNER JOIN table5 AS t5 ON t1.row4 = t5.row4 
WHERE ... 

這個特殊情況正在導致我的問題。它給了我一個錯誤 - 'on子句'中的未知列「t1.row3」。我不知道是否可以選擇多個表，但在其中一個表上進行內部連接。

Answer 1

的JOIN操作數比逗號,操作更高的優先級，因此連接是有效地視爲

t1, t2, (t3, t4, t5 ON ...) 

各地T1，T2，T3認沽括號。

SELECT * 
FROM (table1 AS t1, table2 AS t2, table3 AS t3) 
INNER JOIN table4 AS t4 ON t1.row3 = t4.row3 
INNER JOIN table5 AS t5 ON t1.row4 = t5.row4 
WHERE ... 

你也可以寫你的查詢爲：

SELECT * 
FROM table1 AS t1 
INNER JOIN table2 AS t2 
INNER JOIN table3 AS t3 
INNER JOIN table4 AS t4 ON t1.row3 = t4.row3 
INNER JOIN table5 AS t5 ON t1.row4 = t5.row4 
WHERE ... 

因爲逗號等價於INNER JOIN沒有連接條件。