如何使Select Query适应null条件而不是null条件

Question

select first_name,last_name from contacts where first_name = 'somevalue' and last_name = 'somevalue'

我通过ajax获取这些值

示例表联系人

id | first_name | last_name

1  | Rahul      |  Roy
2  | Rohit      |  NULL

现在当通过ajax我得到first_name作为＆＃34; Rahul＆＃34;和last_name为＆＃34; Roy＆＃34;查询返回1条记录（第一条）

但如果我得到first_name作为＆＃34; Rohit＆＃34;并且last_name为空我得到以下查询

select first_name,last_name from contacts where first_name = 'Rohit' and last_name = ''

我没有记录。但实际上我想从上表中获取id为2的记录。

我的查询如何只在一个查询中填满这两个条件

Answer 1

SELECT first_name,last_name 
FROM contacts 
WHERE first_name = 'Rohit' and (last_name IS NULL OR last_name = 'your value')

你走了！

Answer 2

对于这种情况USE NULL，你能试试吗？

select first_name,last_name 
from contacts 
where first_name = 'Rohit' and last_name = ''

到

select first_name,last_name 
from contacts 
where first_name = 'Rohit' 
      and (last_name IS NULL || last_name='somevalue')

如果您希望姓氏不为空

select first_name,last_name 
from contacts 
where first_name = 'Rohit' 
      and last_name IS NOT NULL

Answer 3

使用“is null”而不是“=''”。

即

select first_name,last_name from contacts where first_name = 'Rohit' and last_name is null

Answer 4

select first_name,last_name 
from contacts 
where first_name = 'Rahul' and (last_name = 'Roy' or last_name is null);