Detailed explanation of how thinkphp5 implements query counting function

ThinkPHP is one of the more popular PHP frameworks currently and is widely used, especially in Web back-end development. When using ThinkPHP to develop applications, we often need to query and count data in the database. This article will introduce the query counting of ThinkPHP5 in detail.

1. Query

In ThinkPHP5, we can query the database through the Db class or the Model class. Here we take the Model class as an example.

1. Basic query

We can implement basic query operations through the select() method, as follows:

//创建模型对象
$user = new UserModel();
//查询user表中姓名为张三的记录
$result = $user -> where('name','张三') -> select();

The above code , the where() method is used to specify query conditions, and its parameter format is where(query field, query value). When the query conditions are multiple fields, we can use chain operations.

is as follows:

$user -> where('name','张三') -> where('age',20) -> select();

This means querying the records in the user table whose name is Zhang San and whose age is 20.

2. Conditional query

We can add where(), whereOr(), to the query statement whereLike() and other conditional query methods to achieve more flexible query operations.

is as follows:

//查询user表中年龄大于20，且性别为男的记录
$result = $user -> where('age','>',20) -> where('gender','男') -> select();
//查询user表中年龄小于20或性别为女的记录
$result = $user -> where('age','<&#39;,20) -> whereOr('gender','女') -> select();
//查询user表中姓名包含‘张’的记录
$result = $user -> whereLike('name','%张%') -> select();

In the above code, the where() method and the whereOr() method respectively indicate that the query conditions are "and" and The "or" relationship has the same parameter format; the whereLike() method is used to implement fuzzy query, and its second parameter represents the query matching condition.

In addition, we can also chain call order() to sort the query results, as follows:

$result = $user -> where('age','>',20) -> order('age desc') -> select();

The above code means to query the records whose age is greater than 20 in the user table. And sorted by age from oldest to youngest.

3. Paging query

When we need to query a large amount of data, we can use the paging query function to prevent the server from being overloaded due to excessive data volume.

In ThinkPHP5, we can use the limit() method to implement paging query. limit()The method has two parameters. The first parameter indicates the starting offset, and the second parameter indicates the number of records displayed on each page.

is as follows:

// 每页显示3条记录，查询第2页的数据
$result = $user -> limit(3,3) -> select();

The above code indicates querying page 2 of the user table and displaying 3 records on each page.

2. Counting

In ThinkPHP5, we can implement the basic counting function through the count() method.

is as follows:

//计算user表中记录总数
$count = $user -> count();
//计算user表中年龄大于20的记录数
$count = $user -> where('age','>',20) -> count();

It should be noted that the count() method actually performs a query on the database, so in actual applications, errors should be minimized as much as possible. Necessary counting operations to improve application performance.

3. Summary

In ThinkPHP5, we can implement database query and counting function. When using it, you should pay attention to the reasonable use of query conditions and paging query functions, and minimize unnecessary counting operations to improve application performance.

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