【原】Oracle行转列语法总结大全

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注：本文测试以Oracle 11g下的scoot schema为例。

需求：求emp表各个岗位的工资之和，若无，用0代替。

一、decode语法

SELECT deptno, nvl(SUM(decode(job, 'MANAGER', sal)), 0) s_MANAGER, nvl(SUM(decode(job, 'ANALYST', sal)), 0) s_ANALYST, nvl(SUM(decode(job, 'CLERK', sal)), 0) s_CLERK, nvl(SUM(decode(job, 'PRESIDENT', sal)), 0) s_PRESIDENT, nvl(SUM(decode(job, 'SALESMAN', sal)), 0) s_SALESMAN FROM empGROUP BY deptno;

二、CASE语法

SELECT deptno, nvl(sum(case when job = 'MANAGER' then sal else 0 end),0) s_MANAGER, nvl(sum(case when job = 'ANALYST' then sal else 0 end),0) s_ANALYST, nvl(sum(case when job = 'CLERK' then sal else 0 end),0) s_CLERK, nvl(sum(case when job = 'PRESIDENT' then sal else 0 end),0) s_PRESIDENT, nvl(sum(case when job = 'SALESMAN' then sal else 0 end),0) s_SALESMAN FROM emp GROUP BY deptno;

三、PIVOT语法

WITH p AS (SELECT deptno, job, sal FROM emp)SELECT * FROM p pivot(SUM(sal) FOR job IN('MANAGER' AS s_MANAGER, 'ANALYST' AS s_ANALYST, 'CLERK' AS s_CLERK, 'PRESIDENT' AS s_PRESIDENT, 'SALESMAN' AS s_SALESMAN));

不过这个地方null值没有替换成0，要通过nvl再转换一下。

WITH p AS (SELECT deptno, job, sal FROM emp),tmp AS (SELECT * FROM p pivot(SUM(sal) FOR job IN('MANAGER' AS s_MANAGER, 'ANALYST' AS s_ANALYST, 'CLERK' AS s_CLERK, 'PRESIDENT' AS s_PRESIDENT, 'SALESMAN' AS s_SALESMAN)))SELECT deptno, nvl(s_MANAGER, 0) s_MANAGER, nvl(s_ANALYST, 0) s_ANALYST, nvl(s_CLERK, 0) s_CLERK, nvl(s_PRESIDENT, 0) s_PRESIDENT, nvl(s_SALESMAN, 0) s_SALESMAN FROM tmp

小结：

decode 语法简单，Oracle独有。
case sql标准语法。
pivot 语法最为简单，Oracle、sqlserver、postgresql均可以使用。

下面再来讲讲wm_concat、listagg、xmlagg。

需求：部门编号为20的所有的员工信息，以行的形式显示。

四、wm_contact语法

SELECT T.DEPTNO, wm_concat(t.ename) names FROM EMP T WHERE T.DEPTNO = '20' GROUP BY T.DEPTNO;

五、listagg语法

SELECT T.DEPTNO, listagg(T.ENAME, ',') WITHIN GROUP(ORDER BY T .ENAME) names FROM EMP T WHERE T.DEPTNO = '20' GROUP BY T.DEPTNO;

六、xmlagg语法

SELECT T.DEPTNO, xmlagg(XMLELEMENT(T, ',',T.ENAME) ORDER BY T .ENAME).EXTRACT ('//text()') names FROM EMP T WHERE T.DEPTNO = '20' GROUP BY T.DEPTNO;

小结：

wm_concat 语法最简单，但是默认是 clob列，plsql不容易导出。
listtagg 语法稍微复杂，但是默认是字符串，性能会比wm_concat 好，但是超过4000个字符，受限制。
xmlagg 字符串超过4000字符,就需要使用xmlagg。

作者

曾庆顺，10年数据库运维、数据仓库及大数据经验，擅长Oracle、MySQL、Hive，具有Oracle 10g OCP，Linux RHCE，长期服务于通信、金融信贷行业。

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