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This article will explain in detail what are the advantages and disadvantages of the MERGE table in MySQL. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

Advantages of MERGE:

1. Simply manage log tables. For example, you can put data from different months on different tables and use myisampacl compression. Then create MERGE to use them.

two。 Get faster speed. You can split large read-only tables according to some key points, and then separate multiple tables on different disks. MERGE table structures can be faster than using a single large table.

3. It is more efficient to execute queries. If you know exactly what you want to get, you can execute the query on the underlying table, and then use merge for many other tables. There can be many merge on a set of tables.

4. The repair is more effective. Repairing a small table is faster than repairing a single table.

5. Map the watch to one in time. MERGE tables do not need to be maintained because the indexes belong to individual tables. MERGE can be created or remapped quickly.

6. If you have a set of tables, you need to create a large table first, and now you can use the MERGE table instead.

7. The file size can exceed the system limit because the MERGE consists of multiple tables.

8. You can create an alias by mapping to the MERGE table

Disadvantages of MERGE:

1. You can only use MyISAM as the underlying table.

two。 Some features of the MyISAM table are not available. For example, you cannot create a full-text index.

3. If the MERGE table is not temporary, all low MyISAM tables must be non-temporary. If the MERGE table is temporary, the underlying table may or may not be temporary.

The 4.MERGE table has more file descriptions than MyISAM. If 10 clients map 10 MyISAM tables using the MERGE table. The service uses (10x10) + 10 file descriptions.

5. Index reading is slow. When you read the index, the MERGE storage engine needs to perform a read on all the underlying tables to check which best matches the given index value. To read the next value, the MERGE storage engine needs to query read buffer to find the next value. MERGE indexes are slow on eq_ref, but not slow on ref.

This is the end of this article on "what are the advantages and disadvantages of MERGE table in MySQL". I hope the above content can be helpful to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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