加入了4桌

Question

下面是用模式和樣本查詢小提琴：http://sqlfiddle.com/#!2/573ec4/9

我期待回到C.price使用I.section和L.level，這是通過其他連接獲得。當使用費用的內部連接時，我剩下沒有結果：http://sqlfiddle.com/#!2/573ec4/2

由於成本是一個表格，它將一個部分和層次映射到一個價格，我希望能夠計算出我的所有放映的價格查詢

Answer 1

當你加入到Cost表不包括適當的連接條件：

INNER JOIN `cost` `C` 
    ON `I`.`Section` = c.section -- = c.section is missing 
    AND `L`.`level` = c.level; -- = c.level is missing 

所以你的完整查詢將是：

SELECT `F`.`date`, 
    `F`.`time`, 
    `F`.`tname`, 
    `I`.`section`, 
    `L`.`level`, 
    c.price 
FROM `booking_for_schedule` `F` 
INNER JOIN `booking_in_seats` `I` 
    on `F`.`tname`=`I`.`tname` 
    AND `F`.`booking_num` = `I`.`booking_num` 
INNER JOIN `level` `L` 
    on `F`.`date`=`L`.`date` 
    AND `F`.`time`=`L`.`time` 
    AND `F`.`tname`=`L`.`tname` 
INNER JOIN `cost` `C` 
    ON `I`.`Section` = c.section 
    AND `L`.`level` = c.level; 

見SQL Fiddle with Demo

Answer 2

看起來您缺少INNER JOIN cost C上的某個子句（當您加入Cost表時）。

它應該是這樣的：的

INNER JOIN `cost` `C` ON `I`.`Section`=`C`.`Section` AND `L`.`level`=`C`.`level` 

代替：

INNER JOIN `cost` `C` ON `I`.`Section` AND `L`.`level` 

Answer 3

你已經錯過了加入列。你沒有結果的原因是因爲I.Section AND L.level將始終返回false。

SELECT F.date, 
     F.time, 
     F.tname, 
     I.section, 
     L.level, 
     c.* 
FROM booking_for_schedule F 
     INNER JOIN booking_in_seats I 
      ON F.tname = I.tname AND 
       F.booking_num = I.booking_num 
     INNER JOIN level L 
      ON F.date = L.date AND 
       F.time = L.time AND 
       F.tname = L.tname 
     INNER JOIN cost C 
      ON I.Section = C.Section AND -- <<== HERE 
       L.level = C.level   -- <<== HERE 

• SQLFiddle Demo

Answer 4

你的最後一行的問題是：

INNER JOIN `cost` `C` ON `I`.`Section` AND `L`.`level` 

它應該是這樣的：

INNER JOIN `cost` `C` ON `I`.`Section` = `C`.`Section` AND `L`.`level` = `C`.`Level`