P粉2332954062年前

添加CHECK约束 1.在创建数据表时添加CHECK约束 语法： CREATE TABLE table_name( ..., CONSTRAINT constraint_name CHECK(约束条件) ）； 2.在修改数据表时添加CHECK约束 ALTER TABLE table_name ADD CONSTRAINTS constraint_name CHECK (约束条件) --学生信息表 create table tb_students; stu_num char(5) primary key, stu_name varchar(20), stu_sex char(4), stu_age number(2), stu_tel char(11), constraint ck_student_sex CHEKE(stu_sex='男' or stu_sex='女')， constraint ck_student_age CHEKE(stu_age between 6 and 30) ）； --在创建表后 通过修改表修改表语句来创建CHEKE约束 alter table tb_students add constraints ck_student_sex CHECK(stu_sex='男' or stu_sex='女')； --删除已添加的CHECK约束 语法;(ALTER TABLE table_name DROP CONSTRAINTS constraint_name) ALTER TABLE tb_students drop constraints ck_student_sex;

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