将 DISTINCT 添加到 UNION 查询

Question

我如何从中获得不同的 title.id：

 SELECT Title.id, Title.title FROM titles as Title HAVING points > 0 
 UNION ALL 
 SELECT Title.id, Title.title FROM titles as Title HAVING points > 1

查询还有更多内容，但这应该足以继续下去。

Answer 1

只需删除全部即可。有些风格允许添加 DISTINCT 而不是 ALL 来更加明确，但这是多余的，因为默认总是过滤重复项。

MySQL - http://dev.mysql.com/doc/refman/ 5.0/en/union.html
MSSQL - http://msdn.microsoft.com/en-us/library/ ms180026.aspx
ORACLE - https://docs.oracle.com/cd/ B28359_01/server.111/b28286/queries004.htm
PostgreSQL - http://www.postgresql.org/docs/8.3/ Interactive/queries-union.html
ETC。

Answer 2

简单的方法不是完全去掉并集和第二部分吗：

SELECT Title.id, Title.title FROM titles as Title HAVING points > 0 

因为 HAVINGpoints> 0 包括具有 HAVING 点 > 的任何内容1？

Answer 3

您可以按照其他人的建议删除ALL。

如果两个查询使用相同的表并且仅在 WHERE 子句或仅在 HAVING 子句中不同，您还可以使用以下命令：

SELECT Title.id, Title.title FROM titles as Title
WHERE (1st query conditions)
   OR (2nd query conditions)

或

SELECT Title.id, Title.title FROM titles as Title
HAVING (1st query conditions)
    OR (2nd query conditions)