如何在SQLite中使用select語句更新表

Question

我想借助其他表的外鍵更新一個表。

我試圖做這樣的事情：

UPDATE tbl_1 
SET field1 = 6, field12 = NULL 
WHERE field3 = (SELECT tbl_2.item1 
       FROM tbl_1, tbl_2 
       WHERE tbl_1.field3 = tbl_2.item1 AND tbl_2.item2 = 135) 

OR

UPDATE tbl_1 
SET field1 = 6, field12 = NULL 
WHERE field3 = (SELECT item1 FROM tbl_2 WHERE item2 = 135) 

Answer 1

我認爲以下情況之一將工作中的一項：

UPDATE tbl_1 
SET  field1 = 6, field12 = NULL 
WHERE EXISTS 
     ( SELECT 1 
      FROM tbl_2 
      WHERE tbl_1.field3 = tbl_2.item1 
      AND tbl_2.item2 = 135 
     ) 

OR

UPDATE tbl_1 
SET  field1 = 6, field12 = NULL 
WHERE field3 IN (SELECT item1 FROM tbl_2 WHERE item2 = 135) 

Answer 2

這是因爲SELECT返回多行。做到這一點，而不是：

UPDATE tbl_1 SET field1 = 6, field12 = NULL 
WHERE field3 IN (SELECT item1 FROM tbl_2 WHERE item2 = 135) 

當SELECT收益表（或多行）IN使用。如果您確定內部查詢應該只返回一行，那麼您將不得不相應地調整內部查詢。這樣的左右：

UPDATE tbl_1 SET field1 = 6, field12 = NULL 
WHERE field3 = (SELECT item1 FROM tbl_2 WHERE item2 = 135 ORDER BY myValue LIMIT 1) 

它的安全使用這裏IN「因爲它可以同時處理單個記錄和多個記錄從SELECT語句返回。

Answer 3

對於單值：

UPDATE tbl_1 
SET field1 = 6, field12 = NULL 
WHERE field3 = (SELECT tbl_2.item1 
       FROM tbl_1, tbl_2 
       WHERE tbl_1.field3 = tbl_2.item1 AND tbl_2.item2 = 135) 

多個值

UPDATE tbl_1 
SET field1 = 6, field12 = NULL 
WHERE field3 IN (SELECT tbl_2.item1 
       FROM tbl_1, tbl_2 
       WHERE tbl_1.field3 = tbl_2.item1 AND tbl_2.item2 = 135) 

Answer 4

你可以使用這樣的

UPDATE tbl_1 
SET field1 = 6, field12 = NULL 
WHERE field3 in (SELECT tbl_2.item1 
       FROM tbl_1, tbl_2 
       WHERE tbl_1.field3 = tbl_2.item1 AND tbl_2.item2 = 135) 

sqllite不支持加入更新查詢。所以這是選項

Answer 5

您還可以使用INSERT或REPLACE語句，有點像如下：

假設tbl_1有4列：key，field1，field2，field3
和你想用來自tbl_2的匹配值更新field2

INSERT OR REPLACE INTO tbl_1 
SELECT tbl_1.key, tbl_1.field1, tbl_2.value, tbl_1.field3 
FROM tbl_1 JOIN tbl_2 ON tbl_2.key = tbl_1.key