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POMySQL - Many column in an index? Or one by one?
 

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  1. POMySQL - Many column in an index? Or one by one?
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    <p>Suppose that a product can have up to five (5) complaints. In this case, there is a table with five (5) columns. These five columns directly involved in the other table, where reports claim codes.</p> <p>See in: <a href="http://img263.imageshack.us/img263/4990/01mysql.jpg" rel="nofollow">http://img263.imageshack.us/img263/4990/01mysql.jpg</a></p> <p>From this moment, I have to make a relationship between two tables. So which of the following is more correct to create indexes:</p> <p>a) creating index one by one?</p> <pre><code>ALTER TABLE `complaint` ADD INDEX (`code_01`) ALTER TABLE `complaint` ADD INDEX (`code_02`) ALTER TABLE `complaint` ADD INDEX (`code_03`) ALTER TABLE `complaint` ADD INDEX (`code_04`) ALTER TABLE `complaint` ADD INDEX (`code_05`) </code></pre> <p>b) That all fields in a single index?</p> <pre><code>ALTER TABLE `complaint` ADD INDEX (`code_01`, `code_02`, `code_03`, `code_04`, `code_05`) </code></pre> <p>I believe the best option is a), because if I choose option b) and by accessing "Relation View" in phpMyAdmin, it shows that there are other fields saying that there is "No index defined!" in columns code_02, code_03, and code_04 code_05.</p> <hr> <p>ATTENTION - FOR INSERT AND UPDATE:</p> <p>If I use option b) and enter a code on record with columns code_02, code_03, and code_04 code_05, MySQL does not advise any errors that the code entered does not exist. Only returns a success message which should really be incorrect. So in this particular case, I have to use option a), right?</p>
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    1. USVegetus
    1. USVegetus
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    1. COHave you tried to generate a query plan to see what your DB is doing?
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      1. USFrustratedWithFormsDesigner
    2. COYes, already. What I concluded is that, in addition to answers about the performance, if I use option b) and inserting the rows, MySQL is not able to warn us of the claim that the code does not exist in table B. So, in this case I believe it is recommended to use the option a).
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      1. USVegetus
 

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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

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