Sql编写实例

Sql编写实例：

一、行变列。

create or replace view v_account_detail as
select t.project_id,
       t.pay_year,
       t.pay_quart,
       t.pay_month,
       (case t.catalog
         when '工程施工费' then
         decode(sum(amount), null, 0,sum(amount))

       end) as engineer_cost,
       (case t.catalog
         when '设备费' then
          decode(sum(amount), null, 0,sum(amount))
       end) as equip_cost,
       (case t.catalog
         when '前期工作费' then
          decode(sum(amount), null, 0,sum(amount))
       end) as pre_cost,
       (case t.catalog
         when '工程监理费' then
          decode(sum(amount), null, 0,sum(amount))
       end) as super_cost,
       (case t.catalog
         when '拆迁补偿费' then
          decode(sum(amount), null, 0,sum(amount))
       end) as remove_cost,
       (case t.catalog
         when '竣工验收费' then
          decode(sum(amount), null, 0,sum(amount))
       end) as checke_cost,
       (case t.catalog
         when '业主管理费' then
          decode(sum(amount), null, 0,sum(amount))
       end) as owner_cost
  from (select a.project_id,
               '工程施工费' as catalog,
               to_number(to_char(t.pay_date, 'YYYY')) as pay_year,
               to_number(to_char(t.pay_date, 'Q')) as pay_quart,
               to_number(to_char(t.pay_date, 'mm')) as pay_month,
               amount
          from pay_pre_cost_payment t
          left join pay_pre_cost_apply a
            on a.apply_bill_id = t.apply_bill_id
        union all
        select a.project_id,
               '工程施工费' as catalog,
               to_number(to_char(t.pay_date, 'YYYY')) as pay_year,
               to_number(to_char(t.pay_date, 'Q')) as pay_quart,
               to_number(to_char(t.pay_date, 'mm')) as pay_month,
               amount
          from pay_proc_cost_payment t
          left join pay_proc_cost_apply a
            on a.apply_bill_id = t.apply_bill_id
        union all
        select a.project_id,
               '工程施工费' as catalog,
               to_number(to_char(t.pay_date, 'YYYY')) as pay_year,
               to_number(to_char(t.pay_date, 'Q')) as pay_quart,
               to_number(to_char(t.pay_date, 'mm')) as pay_month,
               amount
          from pay_comp_cost_payment t
          left join pay_comp_cost_apply a
            on a.apply_bill_id = t.apply_bill_id
        union all
        select t.project_id,
               cost_catalog as catalog,
               to_number(to_char(t.pay_date, 'YYYY')) as pay_year,
               to_number(to_char(t.pay_date, 'Q')) as pay_quart,
               to_number(to_char(t.pay_date, 'mm')) as pay_month,
               amount
          from pay_other_cost_payment t) t
 group by t.project_id,t.catalog, t.pay_year, t.pay_quart, t.pay_month;

 知识点：1）view 为视图。

             2）union all 将 查询结果合并（含重复的数据），union 排除重复的。列名可以不同，列的个数必须相同。

             3）group by 除了查询出来的可以求和的sum值以外的所有列作为条件分组。

             4)  left join  on 左外联，左边表的数据全部显示，不管右边表有没有对应的符合条件的数据

             5）to_number(to_char(t.pay_date, 'Q')) as pay_quart 取季度，取数值类型。

             6）行变列，将行中 某一属性作为列 (case t.catalog
         when '工程监理费' then
          decode(sum(amount), null, 0,sum(amount))
       end) as super_cost,

二、表a、表b。a一对多b。俩表关联查询，由上向下查询。例子：显示a的信息同时显示b对应a 中id 相同项目的和。

 select a.id,a.name,(select sum(b.score) from b where b.id = a.id) as totalScorce from a