Paginating Results with LIMIT and OFFSET in MySQL
Jul 05, 2025 am 02:41 AM
MySQL paging is commonly implemented by LIMIT and OFFSET, but its performance is poor under large data volumes. 1. LIMIT controls the number of each page, OFFSET controls the starting position, and the syntax is LIMIT N OFFSET M; 2. Performance problems are caused by excessive records and discarding OFFSET, resulting in low efficiency; 3. Optimization suggestions include using cursor paging, index acceleration, and lazy loading; 4. Cursor paging locates the starting point of the next page through the unique value of the last record of the previous page, avoiding OFFSET, which is suitable for "next page" operations, and is not suitable for random jumps.
Paging is a common requirement when MySQL querying large amounts of data. For example, when the website displays user lists, article lists and other scenarios, usually only a fixed amount of data is displayed on a page. At this time, LIMIT and OFFSET need to be used to achieve pagination.
Basic usage: LIMIT controls the number, OFFSET controls the starting position
MySQL's LIMIT is used to limit the number of records returned by the query, and OFFSET is used to specify which record to return from. The basic syntax is as follows:
SELECT * FROM table_name ORDER BY id LIMIT N OFFSET M;
-
Nis the number of records to be displayed per page; -
Mis to skip the previous records, that is(當(dāng)前頁碼- 1) * N
For example, if you want to obtain the data on page 3 and display 10 pieces per page, you need to write it as:
SELECT * FROM users ORDER BY id LIMIT 10 OFFSET 20;
Note: If there are no appropriate sorting fields in the table, duplicate or missing data may occur between different pages.
Pagination performance problem: The bigger the OFFSET, the slower it is?
When the data volume is very large, using OFFSET may cause performance degradation. Because MySQL actually scans the OFFSET LIMIT bar record and then discards the previous OFFSET bar.
For example:
SELECT * FROM orders ORDER BY created_at DESC LIMIT 10 OFFSET 100000;
Although this statement seems to only take 10 pieces of data, the database actually needs to find out 100,010 pieces first and then throw away the first 100,000 pieces, which is very inefficient.
Optimization suggestions:
- If the pagination is very deep (such as more than 10,000 pages), you can consider using "cursor-based pagination" instead of
LIMIT/OFFSET. - Use indexes to speed up sorting and searches, especially fields that are often used to make paging conditions.
- For scenarios that do not require precise jumps, they can be implemented in a lighter way, such as lazy loading.
Introduction to cursor paging: an efficient solution to replace OFFSET
The so-called "cursor paging" refers to positioning the starting point of the next page by a unique value (such as self-increment ID or timestamp) of the last record of the previous page, thereby avoiding the use of OFFSET .
For example, if id of the last record on the previous page is 12345, then the next page can be written like this:
SELECT * FROM users WHERE id > 12345 ORDER BY id LIMIT 10;
This method does not slow down as the page number becomes deeper, because it is always checked from a specific value.
Applicable premise:
- There must be an ordered and unique field (such as an autoincrement primary key or timestamp).
- It is not suitable for random jumps (such as jumping directly to page 100), but it is more suitable for operations like "next page".
In general, it is simple and common to implement paging with LIMIT and OFFSET , but you should pay attention to performance issues in large data scenarios. If the page is deep or the performance requirements are high, you can consider replacing it with cursor paging and other methods.
The above is the detailed content of Paginating Results with LIMIT and OFFSET in MySQL. For more information, please follow other related articles on the PHP Chinese website!
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Paginating Results with LIMIT and OFFSET in MySQL
Jul 05, 2025 am 02:41 AM
MySQL paging is commonly implemented using LIMIT and OFFSET, but its performance is poor under large data volume. 1. LIMIT controls the number of each page, OFFSET controls the starting position, and the syntax is LIMITNOFFSETM; 2. Performance problems are caused by excessive records and discarding OFFSET scans, resulting in low efficiency; 3. Optimization suggestions include using cursor paging, index acceleration, and lazy loading; 4. Cursor paging locates the starting point of the next page through the unique value of the last record of the previous page, avoiding OFFSET, which is suitable for "next page" operation, and is not suitable for random jumps.
