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原帖由 caizhuoyi 于 2008-7-4 21:14 发表 ![]()
2、行转列
CREATE TABLE t_row_col AS
SELECT id, 'c1' cn, c1 cv
FROM t_col_row
UNION ALL
SELECT id, 'c2' cn, c2 cv
FROM t_col_row
UNION ALL
SELECT id, 'c3' cn, c3 cv FROM t_col_row;
SELECT * FROM t_row_col ORDER BY 1,2;
1)AGGREGATE FUNCTION
适用范围:8i,9i,10g及以后版本
SELECT id,
MAX(decode(cn, 'c1', cv, NULL)) AS c1,
MAX(decode(cn, 'c2', cv, NULL)) AS c2,
MAX(decode(cn, 'c3', cv, NULL)) AS c3
FROM t_row_col
GROUP BY id
ORDER BY 1;
MAX聚集函数也可以用sum、min、avg等其他聚集函数替代。
被指定的转置列只能有一列,但固定的列可以有多列,请看下面的例子:
SELECT mgr, deptno, empno, ename FROM emp ORDER BY 1, 2;
SELECT mgr,
deptno,
MAX(decode(empno, '7788', ename, NULL)) "7788",
MAX(decode(empno, '7902', ename, NULL)) "7902",
MAX(decode(empno, '7844', ename, NULL)) "7844",
MAX(decode(empno, '7521', ename, NULL)) "7521",
MAX(decode(empno, '7900', ename, NULL)) "7900",
MAX(decode(empno, '7499', ename, NULL)) "7499",
MAX(decode(empno, '7654', ename, NULL)) "7654"
FROM emp
WHERE mgr IN (7566, 7698)
AND deptno IN (20, 30)
GROUP BY mgr, deptno
ORDER BY 1, 2;
这里转置列为empno,固定列为mgr,deptno。
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这个今天用到了,不错,解决了问题 |
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