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HomeDatabaseMysql TutorialOracle纵向表转换为横向表写法

Oracle纵向表转换为横向表写法 假设存在如下纵向表,第一列为id(可能是某个业务数据的id),第二列为类型,第三列为类型对应的值

Oracle纵向表转换为横向表写法

假设存在如下纵向表,第一列为id(可能是某个业务数据的id),第二列为类型,第三列为类型对应的值,如下图:

如上表,存在2,3,4三种类型,其中业务数据ID为1的三种类型都有值,业务数据ID为2的三种类型都有值,业务数据ID为3的只有类型2和3有值,现在要把纵向表横过来显示,可以采用如下代码:

 -- =========================================================
-- 纵向表变横向表:
-- 1. 转换类型,类型的值必须是整数,且不等于0,即0没有意义,0可以表示为空
 -- =========================================================
SELECT
      t.id,
      SUM(DECODE(t.code, 2, 2, 0)) "第二项", -- 如果该行类型为2则就是2,其它的都为0
      SUM(DECODE(t.code, 3, 3, 0)) "第三项",
      SUM(decode(t.code, 4, 4, 0)) "第四项"
 FROM ttt t WHERE t.id=1 GROUP BY t.id;
 -- =========================================================
-- 纵向表变横向表:
-- 1. 转换类型对应的数据,且数据需要是数值,且0没有意义,,即0可以表示为空
 -- =========================================================
 SELECT
      t.id,
      SUM(DECODE(t.code, 2, t.val, 0)) "第二项", -- 如果该行类型为2则显示2类型对应的值DECODE,否则都显示0
      SUM(DECODE(t.code, 3, t.val, 0)) "第三项",
      SUM(DECODE(t.code, 4, t.val, 0)) "第四项"
 FROM ttt t GROUP BY t.id;

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