SQL高手篇:精妙SQL语句介绍

核心提示： ·一个sql语句，包含有几乎所有标准查询·经验分享交流：常用SQL语句技法·SQL语句和存储过程 查询语句的流程控·实战SQL语句收集(不断更新中--)·SQL语句性能优化--LECCO SQL Expert·查询同一表内多字段同时重

·一个sql语句，包含有几乎所有标准查询
·经验分享交流：常用SQL语句技法
·SQL语句和存储过程 查询语句的流程控
·实战SQL语句收集(不断更新中--)
·SQL语句性能优化--LECCO SQL Expert
·查询同一表内多字段同时重复记录的SQL
·数据库人员手边系列：SQL语句导入导出
·得出SQL语句的执行时间的方法
·使用一条SQL语句删除表中重复记录
·Transact_SQL小手册(各种sql语句大集

　　说明： 从数据库中去一年的各单位电话费统计(电话费定额贺电化肥清单两个表来源）

　　SQL:

　　SELECT a.userper, a.tel, a.standfee, TO_CHAR(a.telfeedate, 'yyyy') AS telyear, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '01', a.factration)) AS JAN, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '02', a.factration)) AS FRI, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '03', a.factration)) AS MAR, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '04', a.factration)) AS APR, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '05', a.factration)) AS MAY, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '06', a.factration)) AS JUE,SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '07', a.factration)) AS JUL, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '08', a.factration)) AS AGU, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '09', a.factration)) AS SEP, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '10', a.factration)) AS OCT, SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '11', a.factration)) AS NOV,SUM(decode(TO_CHAR(a.telfeedate, 'mm'), '12', a.factration)) AS DEC FROM (SELECT a.userper, a.tel, a.standfee, b.telfeedate, b.factration FROM TELFEESTAND a, TELFEE b WHERE a.tel = b.telfax) a GROUP BY a.userper, a.tel, a.standfee, TO_CHAR(a.telfeedate, 'yyyy') 　　

　　说明：四表联查问题：

　　SQL: select * from a left inner join b on a.a=b.b right inner join c on a.a=c.c inner join d on a.a=d.d where ..... 　　

　　说明：得到表中最小的未使用的ID号

　　SQL:

　　SELECT (CASE WHEN EXISTS(SELECT * FROM Handle b WHERE b.HandleID = 1) THEN MIN(HandleID) + 1 ELSE 1 END) as HandleID FROM Handle WHERE NOT HandleID IN (SELECT a.HandleID - 1 FROM Handle a)