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  • 01 SQL核心语句

    在 sqlplus 中可以使用 ; 或 / 来执行一条 sql 语句, 但是 / 必须要换行, 个人感觉只有那些脚本啊什么的最后一般使用 / , 其他的都使用;

    核心语句

    SELECT

    oracle 基于查询成本的优化器(cost-based optimizer, CBO) 用来产生实际的执行计划.  SQL 语句的执行顺序

    5  select *

    1  from tablename

    2  where

    3  group by

    4  having

    6  order by

    INSERT

    直接介绍多表插入

       1:  insert all
       2:      when sum_orders < 10000 then
       3:          into small_customers
       4:      when sum_orders >= 10000 and sum_orders < 100000 then
       5:          into medium_customers
       6:      else
       7:          into large_customers
       8:  select customer_id, sum(order_total) sum_orders
       9:  from oe.orders
      10:  group by customer_id;
      11:   
      12:  -- 注意上例是仿照
      13:  insert into scott.bonus(ename, job, sal)
      14:  select ename, job, sal from scott.emp;

    UPDATE

    -- example 2 使用子查询作为修改的值

       1:  update employees2
       2:  set (salary, first_name) = ( select salary * 10, last_name
       3:                                   from employees
       4:                               where employees.employee_id = employees2.employee_id)
       5:  where department_id = 90;

    DELETE

       1:  delete from (select * from employees2 where department_id = 90);

    MERGE

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  • 原文地址:https://www.cnblogs.com/moveofgod/p/3656387.html
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