Oracle 列转行函数 Listagg()

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原文:http://dacoolbaby.iteye.com/blog/1698957

这是一个Oracle的列转行函数:LISTAGG()

先看示例代码

  1. withtempas(
  2. select'China'nation,'Guangzhou'cityfromdualunionall
  3. select'China'nation,'Shanghai'cityfromdualunionall
  4. select'China'nation,'Beijing'cityfromdualunionall
  5. select'USA'nation,'NewYork'cityfromdualunionall
  6. select'USA'nation,'Bostom'cityfromdualunionall
  7. select'Japan'nation,'Tokyo'cityfromdual
  8. )
  9. selectnation,listagg(city,',')withinGROUP(orderbycity)
  10. fromtemp
  11. groupbynation

这是最基础的用法

LISTAGG(XXX,XXX) WITHIN GROUP( ORDER BY XXX)

用法就像聚合函数一样,通过Group by语句,把每个Group的一个字段,拼接起来。

非常方便。

同样是聚合函数,还有一个高级用法

就是over(partition by XXX)

也就是说,在你不实用Group by语句时候,也可以使用LISTAGG函数

  1. withtempas(
  2. select500population,'China'nation,'Guangzhou'cityfromdualunionall
  3. select1500population,'Shanghai'cityfromdualunionall
  4. select500population,'Beijing'cityfromdualunionall
  5. select1000population,'USA'nation,'NewYork'cityfromdualunionall
  6. select500population,'Bostom'cityfromdualunionall
  7. select500population,'Japan'nation,'Tokyo'cityfromdual
  8. )
  9. selectpopulation,
  10. nation,
  11. city,
  12. listagg(city,')withinGROUP(orderbycity)over(partitionbynation)rank
  13. fromtemp

总结:LISTAGG()把它当作SUM()函数来使用就可以了。

原文链接:https://www.f2er.com/oracle/208675.html

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