[Solved] Will I see performance gains by creating table relationships?
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Will I see performance gains by creating table relationships?

I understand the benefits of using table relationships in order to create constraints, such as preventing a row from being deleted from one table when it is related to a row in another.

But will doing so improve performance when running joined queries.

Eg. suppose I have InnoDB tables USER and USERINFO as shown below:

    USER
   |Field   |Type        |Null  |Key    |Default          |Extra
 --|id      |int(11)     |NO    |PRI    |                 |auto_increment
|  |email   |varchar(700)|NO    |       |                 |
|  |password|varchar(255)|NO    |       |                 |
|  |active  |varchar(1)  |NO    |       |n                |
|  |created |timestamp   |NO    |       |CURRENT_TIMESTAMP|
|
|   USERINFO
|  |Field   |Type        |Null  |Key    |Default          |Extra
 --|user    |int(11)     |NO    |PRI    |                 |
   |name    |varchar(100)|NO    |       |                 |
   |position|varchar(100)|NO    |       |                 |
    ...

Is it beneficial in terms of performance when running the following query?

SELECT * FROM USER U JOIN USERINFO UI ON U.id = UI.user

How to optimize this SQL query?

The following recommendations will help you in your SQL tuning process.
You'll find 3 sections below:

  1. Description of the steps you can take to speed up the query.
  2. The optimal indexes for this query, which you can copy and create in your database.
  3. An automatically re-written query you can copy and execute in your database.
The optimization process and recommendations:
  1. Avoid Selecting Unnecessary Columns (query line: 2): Avoid selecting all columns with the '*' wildcard, unless you intend to use them all. Selecting redundant columns may result in unnecessary performance degradation.
  2. Create Optimal Indexes (modified query below): The recommended indexes are an integral part of this optimization effort and should be created before testing the execution duration of the optimized query.
Optimal indexes for this query:
ALTER TABLE `USERINFO` ADD INDEX `userinfo_idx_user` (`user`);
The optimized query:
SELECT
        * 
    FROM
        USER U 
    JOIN
        USERINFO UI 
            ON U.id = UI.user

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* original question posted on StackOverflow here.