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SQL: Never uses LIKE unless stricted necessary.


Demand

MUST use "=" (equals sign) instead "LIKE" (like command) whenever "%" (percent sign) is NOT necessary

Description

In MySQL, the "LIKE" operator behaves similarly to "=" (equals sign) when the "%" (percent sign) wildcard is not utilized.

Employing "LIKE" in most of the modern SGDBs (e.q. MySQL) results in the use of a more complex query structures.

The examples below illustrate this. The first query does not use the "%" modifier and is compared to the second, which does. Both provide the same search structure. Contrasting these with the last query, which uses only "=", results in a simpler search structure and all have the same output result.

Therefore, if the "%" modifier is not being used in the search, it's preferable to utilize "=" for simpler and more efficient query execution.

Examples

1:  explain SELECT COUNT(1) FROM users WHERE `username` like "mke";  
2:  # id, select_type, table, partitions, type, possible_keys, key, key_len, ref, rows, filtered, Extra
3:  # 1, SIMPLE, users, , range, username, username, 82, , 1, 100.00, Using where; Using index
1: explain SELECT COUNT(1) FROM users WHERE `username` like "mke%";   
2: # id, select_type, table, partitions, type, possible_keys, key, key_len, ref, rows, filtered, Extra
3: # 1, SIMPLE, users, , range, username, username, 82, , 1, 100.00, Using where; Using index

1: explain SELECT COUNT(1) FROM users WHERE `username` = "mke";
2: # id, select_type, table, partitions, type, possible_keys, key, key_len, ref, rows, filtered, Extra
3: 1, SIMPLE, , , , , , , , , , no matching row in const tableExamples explanation
  1. The query with WHERE username LIKE "mke": This uses a "range" type and applies the index to the search.
  2. The query with WHERE username LIKE "mke%": This also utilizes a "range" type but has a higher number of rows scanned due to the use of the "%" modifier.
  3. The query with WHERE username = "mke": This employs a "const" type and directly uses the index for a more straightforward search.

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