mysql - How does the Like operator behave with an empty argument (%%)? -

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using like operator

select first_name, last_name student_details first_name 's%';

will provide name start s.

but 

select first_name, last_name student_details **first_name '%%';**

%% - didn't have string constraints. query returning complete list.

how like %% processed in sql?

can clarify this?

the % sign considered zero-or-more repetition wildcard character in sql. way works pretty same in other areas of computing, can have wide definition , explaination of how works putting in google.

that's why returns all entries in database, because matches if isn't repeated time (by way, same behavior you'll achieve like '%').

the 1 , 1 repetition wildcard in sql represented _.


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