| 以文本方式查看主题 - Foxtable(狐表) (http://foxtable.com/bbs/index.asp) -- 专家坐堂 (http://foxtable.com/bbs/list.asp?boardid=2) ---- union请教 (http://foxtable.com/bbs/dispbbs.asp?boardid=2&id=130717) |
| -- 作者：hbhb -- 发布时间：2019/1/29 23:52:00 -- union请教 大师：用union合成SQL语句时，SQL语句的执行顺序怎样的？各列数据类型由那句SQL定义？ |
| -- 作者：有点甜 -- 发布时间：2019/1/30 11:00:00 --
第一句的select语句定义列名。
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| -- 作者：hbhb -- 发布时间：2019/1/30 12:00:00 -- 不会吧，好像是无数据的s___elect语句决定的，比如下面的语句，最后一条语句没有数据，但他好像决定每列的数据类型？ S__E---LECT \'单位\' AS xmdlname, cast(traderid as varchar) AS xmindexid, code AS xmid,name AS xmname,\'\' as other1 FROM l_trader union S__E---LECT \'部门\' AS xmdlname, cast(departmentid as varchar) AS xmindexid, code AS xmid,name AS xmname,\'\' as other1 FROM l_department union S__E---LECT \'职员\' AS xmdlname, cast(l_employ.empid as varchar) AS xmindexid, l_employ.code AS xmid, l_employ.name AS xmname, l_department.name AS other1 FROM l_employ INNER JOIN l_department ON l_employ.departmentid = l_department.departmentid union S___E---LECT \'项目\' AS xmdlname, cast(projectid as varchar) AS xmindexid , cast(projectid as varchar) AS xmid,name AS xmname,\'项目\' as other1 FROM al_project union S___E---LECT \'货品\' AS xmdlname, \'g_\' + ltrim(str(goodsid)) AS xmindexid,cast(code as varchar) AS xmid,name AS xmname,\'贷品\' as other1 FROM l_goods |
| -- 作者：有点甜 -- 发布时间：2019/1/30 13:36:00 -- 具体实例发上来测试。 |