MySQL学习笔记六

MySQL学习笔记六

文章目录

一、简介

时隔多日没有学习MySQL数据库了，今天重新开始继续学习MySQL数据库的有关内容，并重新开启MySQL的新的征程。

二、MySQL NULL 值处理

MySQL NULL 值处理

root@host# mysql -u root -p password;
Enter password:*******
mysql> use RUNOOB;
Database changed
mysql> create table runoob_test_tbl
    ->(-> runoob_author varchar(40) NOT NULL,-> runoob_count  INT
    ->);
Query OK,0 rows affected (0.05 sec)
mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('RUNOOB',20);
mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('菜鸟教程', NULL);
mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('Google', NULL);
mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('FK',20);
 
mysql> SELECT *from runoob_test_tbl;+---------------+--------------+| runoob_author | runoob_count |+---------------+--------------+| RUNOOB        |20|| 菜鸟教程  | NULL         || Google        | NULL         || FK            |20|+---------------+--------------+4 rows inset(0.01 sec)

root@host# mysql -u root -p password;
Enter password:*******
mysql> use RUNOOB;
Database changed
mysql> create table runoob_test_tbl
    ->(-> runoob_author varchar(40) NOT NULL,-> runoob_count  INT
    ->);
Query OK,0 rows affected (0.05 sec)
mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('RUNOOB',20);
mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('菜鸟教程', NULL);
mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('Google', NULL);
mysql> INSERT INTO runoob_test_tbl (runoob_author, runoob_count) values ('FK',20);
 
mysql> SELECT *from runoob_test_tbl;+---------------+--------------+| runoob_author | runoob_count |+---------------+--------------+| RUNOOB        |20|| 菜鸟教程  | NULL         || Google        | NULL         || FK            |20|+---------------+--------------+4 rows inset(0.01 sec)

mysql> SELECT * FROM runoob_test_tbl WHERE runoob_count = NULL;
Empty set(0.00 sec)
mysql> SELECT * FROM runoob_test_tbl WHERE runoob_count != NULL;
Empty set(0.01 sec)

mysql> SELECT * FROM runoob_test_tbl WHERE runoob_count IS NULL;+---------------+--------------+| runoob_author | runoob_count |+---------------+--------------+| 菜鸟教程  | NULL         || Google        | NULL         |+---------------+--------------+2 rows inset(0.01 sec)
 
mysql> SELECT *from runoob_test_tbl WHERE runoob_count IS NOT NULL;+---------------+--------------+| runoob_author | runoob_count |+---------------+--------------+| RUNOOB        |20|| FK            |20|+---------------+--------------+2 rows inset(0.01 sec)

三、MySQL 正则表达式

MySQL 正则表达式

MySQL 正则表达式

mysql> SELECT name FROM person_tbl WHERE name REGEXP '^st';

mysql> SELECT name FROM person_tbl WHERE name REGEXP 'ok$';

mysql> SELECT name FROM person_tbl WHERE name REGEXP 'mar';

mysql> SELECT name FROM person_tbl WHERE name REGEXP '^[aeiou]|ok$';

四、总结

以上就是一些有关Mysql的知识，后续还会继续更新的，谢谢大家的阅读与支持了啦，期待大家的持续的支持了啦。