SQL 根据表 2 中的值逐行更新表 1

Question

我有两个 table，我想 UPDATE 一个 table 基于另一个 table 的值。在以下 SO-post 的帮助下，我编写了一个查询：

query = f""" UPDATE table1
             SET goal = 
            (SELECT table2.goal FROM table2                                                                    
             WHERE player = table2.player
                AND opponent = table2.opponent
                AND date = table2.date
                AND competition = table2.competition
                AND score = table2.score """

当我执行查询时，table1 的每一行都会受到 goal 相同值的影响。但是，所需的过程是查询逐行检查是否有匹配的行，如果有，则更新列 goal。我做错了什么？

Answer 1

据我了解，如果 table2 具有相同的值，则此查询只会影响 table1。您要检查是否有任何行相同然后更新目标值吗？

您可以使用 OR 而不是使用 AND。如果任何值相似，此修改将确保查询将通过。

query = f""" UPDATE table1
         SET goal = 
        (SELECT table2.goal FROM table2                                                                    
         WHERE player = table2.player
            OR opponent = table2.opponent
            OR date = table2.date
            OR competition = table2.competition
            OR score = table2.score )"""

Answer 2

您必须将子查询与您要更新的 table 相关联：

UPDATE table1 AS t1
SET goal = (
  SELECT t2.goal 
  FROM table2 AS t2                                                                    
  WHERE t2.player = t1.player
    AND t2.opponent = t1.opponent
    AND t2.date = t1.date
    AND t2.competition = t1.competition
    AND t2.score = t1.score
);

或者：

UPDATE table1 AS t1
SET goal = (
  SELECT t2.goal 
  FROM table2 AS t2                                                                    
  WHERE (t2.player, t2.opponent, t2.date, t2.competition, t2.score) = 
        (t1.player, t1.opponent, t1.date, t1.competition, t1.score)
);

请注意，如果 table1 中的一行与 table2 中的任何行都不匹配，则该列将更新为 null。
如果在这种情况下您不想更新该列，还可以使用 COALESCE():

UPDATE table1 AS t1
SET goal = COALESCE((
  SELECT t2.goal 
  FROM table2 AS t2                                                                    
  WHERE (t2.player, t2.opponent, t2.date, t2.competition, t2.score) = 
        (t1.player, t1.opponent, t1.date, t1.competition, t1.score)
), goal);

如果你的 SQLite 版本是 3.33.0+，你可以使用 UPDATE..FROM 语法：

UPDATE table1 AS t1
SET goal = t2.goal 
FROM table2 AS t2                                                                    
WHERE (t2.player, t2.opponent, t2.date, t2.competition, t2.score) = 
      (t1.player, t1.opponent, t1.date, t1.competition, t1.score);

SQL 根据表 2 中的值逐行更新表 1

SQL UPDATE table1 row-by-row based on values in table2

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sqlite

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