Question

I am using MySQL and I would like to know what exactly happens (or what may happens) in the following cases when I run SLQ queries as-like

Case 1

SELECT ... 
WHERE 'articles'.'author_id' = 2 
  AND (articles.id IN (46,4,5)) 
  AND (articles.id IN (4,5,16,40))

Case 2

SELECT ... 
WHERE 'articles'.'author_id' = 2 
  AND (articles.id NOT IN (46,4,5)) 
  AND (articles.id IN (4,5,16,40))

?

In particular, I mean what happens with doubles articles.id statements in the WHERE clause?

Answer 1

Is just a logical AND

1 && 1 = 1
0 && 1 = 0
1 && 0 = 0
0 && 0 = 0

Applied to the 1. case:

Value        IN (46,4,5)  AND  IN (4,5,16,40)    Result
4                 1                  1             1
5                 1                  1             1
46                1                  0             0
16                0                  1             0
40                0                  1             0

Applied to the 2. case:

Value     NOT IN (46,4,5)  AND  IN (4,5,16,40)   Result
4                 0                  1             0
5                 0                  1             0
46                0                  0             0
16                1                  1             1
40                1                  1             1