UNION ALL 的替代选项答案

【问题标题】：Alternative option to UNION ALLUNION ALL 的替代选项
【发布时间】：2016-09-22 01:26:16
【问题描述】：

我有下面的 SQL：

SELECT '1.1' AS column_a, '1' as column_b, 4 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '1.2' AS column_a, '1' as column_b, 4001 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.1' AS column_a, '2' as column_b, 1 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.1' AS column_a, '2' as column_b, 2 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.1' AS column_a, '2' as column_b, 3 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 1001 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 1002 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 1003 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 1004 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 1005 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 1006 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 2001 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 2002 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 2003 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '2.2' AS column_a, '2' as column_b, 2004 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '3.1' AS column_a, '3' as column_b, 3001 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '3.1' AS column_a, '3' as column_b, 3002 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '3.2' AS column_a, '3' as column_b, 3003 AS column_c FROM SYSIBM.SYSDUMMY1
UNION ALL
SELECT '3.2' AS column_a, '3' as column_b, 3004 AS column_c FROM SYSIBM.SYSDUMMY1

SQL 的结果是固定的，所有的值都是一样的。

我正在使用 DB2。有没有更好的方法来做同样的事情，而不需要在 SQL 中重复那么多？

【问题讨论】：

你可以使用VALUES，比如VALUES ('A', 1), ('B', 2), ('C', 2)
DB2 的平台和版本是什么？
如何查看 DB2 的版本？
当我执行 SELECT GETVARIABLE('SYSIBM.VERSION') FROM SYSIBM.SYSDUMMY1 时得到结果“DSN10015”
他正在使用 db2 10 for zOS

标签： sql db2 union union-all

【解决方案1】：

正如 Lashane 所评论的，如果您的平台和 DB2 版本支持 VALUES，它可能就是答案。

这适用于 DB2 for i v7.1

with tbl (col1,col2) 
  as (VALUES ('A', 1), ('B', 2), ('C', 2))
select * from tbl

【讨论】：

我相信我的 DB2 版本不支持它。我收到错误：非法符号“TBL”。一些可能是合法的符号是：DSN_INLINE_OPT_HINT
@Daniel 你正在使用 db2 10 for zOS 你的版本支持它你只需要正确的语法。
@daniel -- 看我的回答。
不，这里的 VALUES 用法不适用于 DB2/zOS。您必须使用 SYSIBM.SYSDUMMY1 和 UNION 或使用下面的 XMLTABLE 技术。

【解决方案2】：

您可以使用PureXML 将嵌入的 XML 块解析为表格：

SELECT * 
FROM XMLTABLE (
'/set/row'
PASSING XMLPARSE(
'<set>
<row a="1.1" b="1" c="4"/>
<row a="1.2" b="1" c="4001"/>
<row a="2.1" b="2" c="1"/>
</set>')
COLUMNS
column_a CHAR(3) PATH '@a',
column_b CHAR(1) PATH '@b',
column_c INTEGER PATH '@c'
) AS X

【讨论】：