DB2数据库查询

好记性不如写一遍，复习用

1：普通查询

SELECT
    THIRDSYSTIME AS 交易时间,AMOUNT  AS 交易金额,AUTHORCODE  AS 交易码, FEE  AS 手续费,SYSSERNO AS 系统跟踪号
FROM T_CPS_CUPSICACINFO;

2：筛选查询

SELECT
    THIRDSYSTIME AS 交易时间,AMOUNT  AS 交易金额,AUTHORCODE  AS 交易码, FEE  AS 手续费,SYSSERNO AS 系统跟踪号
FROM T_CPS_CUPSICACINFO
WHERE  AMOUNT>=900.00

筛选查询主要有：

=【等于】

!=、<>【不等于】

>【大于】

<【小于】

>=【大于等于】

<=【小于等于】

3：特殊关键字筛选

Like【not like】;in【not in】;between...and【not between...and】;is null【not is null】

Like【模糊查询】

_:代表一个字符;

%:代表任意个字符

SELECT
    THIRDSYSTIME AS 交易时间,AMOUNT  AS 交易金额,AUTHORCODE  AS 交易码, FEE  AS 手续费,SYSSERNO AS 系统跟踪号
FROM T_CPS_CUPSICACINFO
WHERE  AUTHORCODE like '32%'

SELECT
    THIRDSYSTIME AS 交易时间,AMOUNT  AS 交易金额,AUTHORCODE  AS 交易码, FEE  AS 手续费,SYSSERNO AS 系统跟踪号
FROM T_CPS_CUPSICACINFO
WHERE  AUTHORCODE like '3_2%';

IN【匹配查询】

SELECT
    THIRDSYSTIME AS 交易时间,AMOUNT  AS 交易金额,AUTHORCODE  AS 交易码, FEE  AS 手续费,SYSSERNO AS 系统跟踪号
FROM T_CPS_CUPSICACINFO
WHERE  FEE in (9.00,4.00)

between...and...【区间查询】要为小写

SELECT
    THIRDSYSTIME AS 交易时间,AMOUNT  AS 交易金额,AUTHORCODE  AS 交易码, FEE  AS 手续费,SYSSERNO AS 系统跟踪号
FROM T_CPS_CUPSICACINFO
WHERE  FEE  between  1.00 and 2.00

4:逻辑筛选

And;or;not

SELECT
    THIRDSYSTIME AS 交易时间,AMOUNT  AS 交易金额,AUTHORCODE  AS 交易码, FEE  AS 手续费,SYSSERNO AS 系统跟踪号
FROM T_CPS_CUPSICACINFO
WHERE  FEE>= 1.00 and FEE<=2.00

or【】

SELECT
    THIRDSYSTIME AS 交易时间,AMOUNT  AS 交易金额,AUTHORCODE  AS 交易码, FEE  AS 手续费,SYSSERNO AS 系统跟踪号
FROM T_CPS_CUPSICACINFO
WHERE  FEE>= 9.00 or FEE<=1.00

5：分组查询  Group by

SELECT
     FEE  AS 手续费,count(FEE) AS 总数,avg(AMOUNT) AS 平均交易金额
FROM T_CPS_CUPSICACINFO
group by FEE

where   group by

SELECT
     FEE  AS 手续费,count(FEE) AS 总数,avg(AMOUNT) AS 平均交易金额
FROM T_CPS_CUPSICACINFO  where FEE>=5.00
group by FEE

where   group by  having

SELECT
     FEE  AS 手续费,count(FEE) AS 总数,avg(AMOUNT) AS 平均交易金额
FROM T_CPS_CUPSICACINFO  where FEE>=5.00
group by FEE having avg(AMOUNT)>500.00

注意：where;group by;having的执行顺序

Where用于筛选有from指定的数据对象；

Group by 用于对where或from的结果进行分组

Having是对group by的分组数据再进行过滤

With rollup 函数

SELECT
     FEE  AS 手续费,count(FEE) AS 总数,avg(AMOUNT) AS 平均交易金额
FROM T_CPS_CUPSICACINFO
group by FEE  with rollup

6:排序查询

Order by desc【降序】

Order by asc【默认升序】

SELECT
     FEE  AS 手续费,count(FEE) AS 总数,avg(AMOUNT) AS 平均交易金额
FROM T_CPS_CUPSICACINFO where fee>=5.00
group by FEE  order by FEE desc

7： 其他常用聚集函数

Sum【求和】

Avg【平均值】

Max【最大值】

Min【最小值】

Count【行数】

8：子查询

子查询的使用地方相当多，在select,insert,update,delete命令中允许是一个表达式的地方都可以包含子查询

以分页查询为例：

SELECT THIRDSYSTIME AS 交易时间, AMOUNT  AS 交易金额,FEE  AS 手续费,SYSSERNO AS 系统跟踪号
FROM
    (SELECT T_CPS.*,ROWNUMBER() OVER() AS RNUM  FROM
             (SELECT * FROM T_CPS_CUPSICACINFO) AS T_CPS) AS A
WHERE
A.RNUM BETWEEN 10 AND 20;