综述

• 使用 UPDATE 语句更新数据。
• 可以一次更新多条数据。
• 基本套路

UPDATE      table
SET     column = value [,column = value,...]
[WHERE      condition];

基本应用

• 使用 WHERE 子句指定需要更新的数据。

UPDATE employees SET department_id = 70 WHERE employee_id = 113;
1 row updated.

• 如果省略WHERE子句，则表中的所有数据都将被更新。

UPDATE copy_emp SET department_id = 110;
22 rows updated.

sql> ed
Wrote file afiedt.buf

  1* update emp set sal = 1800,deptno = 20 where ename='SMITH'
sql> /

在UPDATE语句中使用子查询

• 更新 114号员工的工作和工资使其与 205号员工相同

UPDATE employees SET job_id = (SELECT job_id FROM employees WHERE employee_id = 205),salary = (SELECT salary FROM employees WHERE employee_id = 205) WHERE employee_id = 114;
1 row updated.

• 在 UPDATE 中使用子查询，使更新基于另一个表中的
  数据。

UPDATE copy_emp SET department_id = (SELECT department_id FROM employees WHERE employee_id = 100) WHERE job_id = (SELECT job_id FROM employees WHERE employee_id = 200);
1 row updated.

更新中的数据完整性错误

UPDATE employees SET department_id = 55 WHERE department_id = 110;


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UPDATE employees * ERROR at line 1: ORA-02291: integrity constraint (HR.EMP_DEPT_FK) violated - parent key not found