Assume the table structure

The user {
U_id pk
}

SignIn {
S_id pk
The date
U_id fk1 - fk
}

I need to query the user
1. In 2019-1-13, and 2019-1-13 users have signIn
2. No signIn the line s_id should be NULL

How to query, can do it, now I in addition to code is used to implement logic, and SQL really don't know how to use the simultaneous to make 2 set up, maintain a null line

CodePudding user response:

Please enter a string length is at least 6

CodePudding user response:

Please enter a string length is at least 6

CodePudding user response:

You show some two tables of content
And then give out the result you want
Best to create table statements, INSERT statements are written out, convenient others to help you

CodePudding user response:

Directly to the left the right side of the join table no data should be null by default

CodePudding user response:

 
Select a t1. The uid, t2. Sid the from user t1 left join (
Select the sid, uid from signIn where the date between startDate and endDate 
) t2 on t1. The uid=t2. The uid.