如何根据另一个表中的值过滤SQL查询

Question

I'm new to SQL queries and are trying to figure out how to filter my output somehow.

The function I want to achieve is that multiple users can be listed as authors on a single entry, AND, also the possibility to filter the search result by using a drop-down menu or something like that to see which entries an author is listed too.

I currently have two tables in my database, one is called ENTRIES and the other is AUTHORS

Each of the tables looks like this:

+-------------------------------+       +---------------------------------+
DB: ENTRIES // To keep all entries.     DB: AUTHORS // To keep track of which authors that are listed to each entry.
+-------------------------------+       +---------------------------------+
ID   TITLE    DATE                      ID   AUTHOR1    AUTHOR2    AUTHOR3
1    NAME     2018-03-19                1    TRUE       FALSE      TRUE
2    NAME     2018-03-20                2    FALSE      TRUE       FALSE
3    NAME     2018-03-21                3    TRUE       FALSE      FALSE
+-------------------------------+       +---------------------------------+

My SQL query looks like this right now:

$query = "
 SELECT * FROM ENTRIES INNER JOIN AUTHORS ON ENTRIES.ID=AUTHORS.ID;
 ";
}
$result = mysqli_query($con, $query);

I get it to list all the results but I don't know how to filter the results based on the value in the AUTHORS table? And are INNER JOIN the right way to go?

The result should be something like:

FILTER ON: ALL / NAME / NAME / NAME

#####################################################
# 1  TITLE     AUTHOR 1 AUTHOR 3         DATE       #
#####################################################

#####################################################
# 2  TITLE     AUTHOR 2                  DATE       #
#####################################################

#####################################################
# 3  TITLE     AUTHOR 1                  DATE       #
#####################################################

Answer 1

You have to use subqueries.

SELECT * FROM entries e
WHERE EXISTS(SELECT id FROM authors a WHERE e.id = a.id)

https://dev.mysql.com/doc/refman/5.7/en/subqueries.html