基于MySQL中的NULL值在新列中显示自定义文本?

让我们首先创建一张表 –

mysql> create table DemoTable1953
  (
  StudentName varchar(20)
  );
Query OK, 0 rows affected (0.00 sec)

使用插入命令在表中插入一些记录 –

mysql> insert into DemoTable1953 values('Chris');
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1953 values(NULL);
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1953 values('David');
Query OK, 1 row affected (0.00 sec)
mysql> insert into DemoTable1953 values(NULL);
Query OK, 1 row affected (0.00 sec)

使用select语句显示表中的所有记录 –

mysql> select * from DemoTable1953;

这将产生以下输出 –

+-------------+
| StudentName |
+-------------+
| Chris       |
| NULL        |
| David       |
| NULL        |
+-------------+
4 rows in set (0.00 sec)

以下是在新列中显示自定义文本的查询的基础上的MySQL语句 –

mysql> select StudentName,IF(StudentName IS NULL,'Student Name Is Not Found','Student Name Found') as Name from DemoTable1953;

这将产生以下输出 –

+-------------+---------------------------+
| StudentName | Name                      |
+-------------+---------------------------+
| Chris       | Student Name Found         |
| NULL        | Student Name Is Not Found  |
| David       | Student Name Found         |
| NULL        | Student Name Is Not Found  |
+-------------+---------------------------+
4 rows in set (0.00 sec)