thinkphp M method multi-table query is an efficient data processing method, which can help us process the relationship between multiple data tables at the same time. This article will introduce how to use this method to implement multi-table queries.

1. What is multi-table query?
In the database, sometimes we need to query the data relationships between multiple data tables, which requires the use of multi-table queries. In general, we can use multiple SELECT statements to implement multi-table queries, but this method will be very slow when processing large amounts of data, so we need to use a more efficient way to perform multi-table queries.

2. Implementation of multi-table query using thinkphp M method
In thinkphp, we can use M method to implement multi-table query. The M method is an efficient ORM (Object Relational Mapping) method, which can help us encapsulate SQL statements to make data processing more convenient.

1. Basic usage:
Using the M method to perform multi-table queries is very simple. We only need to pass in multiple table names when using the M method to implement multi-table queries.

For example, we have two data tables: user and order. Now we need to query the data relationship in the user table and order table. We can do this:

$user_order?=?M('User')->table(array('user'=>'u','order'=>'o'))->where('u.id?=?o.user_id')->select();

In the above code, we use Use the table method and pass in multiple table names, use the where method to specify the relationship between the two data tables, and finally use the select method to obtain the query results.

2. Multi-condition query:
When performing multi-table query, we usually need to specify multiple query conditions. We can use string splicing to implement multi-condition query, or we can use array way to implement multi-condition query.

For example, we need to query the users whose gender is male (gender=1) in the user table and the order information in the user table. We can do this:

$user_order?=?M('User')->table(array('user'=>'u','order'=>'o'))->where(array('u.gender'=>1,'u.id=o.user_id'))->select();

In the above code, we use The where method passes in the query condition array, which contains two query conditions, one of which is to query for male users, and the other is to query order information.

3. Multi-table sorting:
When performing multi-table queries, we sometimes need to sort the query results. We can use the order method to sort multi-tables.

For example, we need to query the users in the user table and the orders in the order table, and sort them according to the order amount. We can do this:

$user_order?=?M('User')->table(array('user'=>'u','order'=>'o'))->where('u.id=o.user_id')->order('o.amount?desc')->select();

In the above code, we use the order method And the sorting condition is passed in, which is sorted according to the order amount.

3. Summary
This article introduces the basic usage of thinkphp M method multi-table query, including basic usage, multi-condition query and multi-table sorting. In actual development, we can use this method flexibly according to actual needs to process data more efficiently.

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