Pagination query mysql statement

In the database, we often need to perform paging queries on the data, control the number displayed on each page, and return the corresponding results.

MySQL provides a very simple way to perform paging queries, using the LIMIT and OFFSET keywords.

LIMIT defines how many rows of records are returned from the query results, and OFFSET defines the row from which the results are returned. For example:

SELECT * FROM table_name LIMIT 10 OFFSET 20;

The above statement will return the 21st to 30th rows of data from table table_name.

If we want to display data from 1 to 10 rows, just use LIMIT directly:

SELECT * FROM table_name LIMIT 10;

MySQL also provides another use The LIMIT method uses two parameters to specify the number of records to be returned and the starting line number. For example:

SELECT * FROM table_name LIMIT 20, 10;

The above statement will return the 21st to 30th rows of data from table table_name.

In addition to the LIMIT and OFFSET keywords, you can also use the ROW_NUMBER() function for paging queries. This function is widely used in SQL Server and Oracle databases, but is not very common in MySQL.

Using this function for paging query requires sorting the query results first, and then adding the ROW_NUMBER() function. For example:

SELECT *, ROW_NUMBER() OVER (ORDER BY column_name) as row_num
FROM table_name
LIMIT 20 OFFSET 0;

The above statement will be in the table table_name by column column_name sorts the results and returns the first 20 rows of data.

In addition to basic paging queries, you can also use some other techniques for paging, such as using INNER JOIN or LEFT JOIN to combine multiple tables to obtain more comprehensive data.

For example, suppose we need to find records that meet specific conditions in two tables. We can use nested queries to limit when INNER JOIN or LEFT JOIN:

SELECT * FROM table_1
INNER JOIN table_2 ON table_1.id = table_2.id
WHERE condition
LIMIT 20 OFFSET 0;

The above statement will find records that meet the conditions in tables table_1 and table_2, and return the first 20 rows of data.

When performing paging queries, we also need to pay attention to some performance and efficiency issues. For example, when using the OFFSET keyword, MySQL needs to scan the entire result set in order to find the records to return.

In order to improve query efficiency, you can use the primary key or unique index to sort the table. This makes queries faster and can use covering indexes to avoid using temporary tables.

In general, when performing paging queries, we should consider the needs of each query by category, and adopt appropriate methods to improve query efficiency and ensure the accuracy of query results.

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