sqlite - SQLite 中的一个查询中的多个 Select 语句

Question

是否可以在 SQLite 的一个查询中运行多个选择语句？

如：

SELECT ( 
           SELECT ChestGemEffects.Value,
                  Effect.Name
             FROM ChestGemEffects
                  INNER JOIN Effect
                          ON ChestGemEffects.EffectId = Effect.Id
                  INNER JOIN Gems
                          ON ChestGemEffects.GemId = Gems.Id
            WHERE ( Gems.[Key] = 'SG1' )  
       ) 
       AS ChestEffects,
       ( 
           SELECT WeaponGemEffects.Value,
                  Effect.Name
             FROM WeaponGemEffects
                  INNER JOIN Effect
                          ON WeaponGemEffects.EffectId = Effect.Id
                  INNER JOIN Gems
                          ON WeaponGemEffects.GemId = Gems.Id
            WHERE ( Gems.[Key] = 'SG1' )  
       ) 
       AS WeaponEffects,
       ( 
           SELECT OthersGemEffects.Value,
                  Effect.Name
             FROM OthersGemEffects
                  INNER JOIN Effect
                          ON OthersGemEffects.EffectId = Effect.Id
                  INNER JOIN Gems
                          ON OthersGemEffects.GemId = Gems.Id
            WHERE ( Gems.[Key] = 'SG1' )  
       ) 
       AS OthersEffects;

它给了我错误：

'执行查询时出错：作为表达式一部分的 SELECT 只允许一个结果'

我的表达有问题还是 SQLite 不支持？

谢谢

Answer 1

必须在子句中使用子查询的结果作为源表进行进一步查询FROM：

SELECT * FROM (SELECT ...), (SELECT ...)

但是，这将是一个cross join，这不是您想要的。

要仅附加多个表（具有相同数量的列），请使用UNION ALL：

SELECT ChestGemEffects.Value,
       Effect.Name
  FROM ...
  ...
UNION ALL
SELECT WeaponGemEffects.Value,
       Effect.Name
  FROM ...
  ...