How to query the sum of two columns of data at the same time in ThinkPHP6?

ThinkPHP6 database query: How to efficiently calculate the sum of jin and chu columns? This article will demonstrate how to use the ThinkPHP6 framework to convert SQL statements select sum(jin),sum(chu) from sysdbuil to the corresponding database query statement, and solve the problem of returning only the single column sum result in the original code.

Many developers may encounter some difficulties when using ThinkPHP6 to process database aggregate functions (such as sum() ). For example, directly using sum() method to try to calculate the sum of multiple columns at the same time often only get partial results.

Error example: The original code tried to use db::table('sysdbuil')->alias('a')->leftjoin(['user' => 'b'], 'a.buil_id = b.id')->sum('a.jin','a.chu'); but this method only returns the sum result of jin column. This is because sum() method can only calculate the sum of one field at a time.

The correct ThinkPHP6 solution:

In order to obtain the sum of the two columns jin and chu at the same time, we need to use field() method to clearly specify the fields to be calculated and wrap them with sum() function:

 Db::table('sysdbuil')->alias('a')
    ->leftJoin(['user' => 'b'], 'a.buil_id = b.id')
    ->field('sum(a.jin) as jin_sum, sum(a.chu) as chu_sum') // Note that the alias is used here ->select();

This code first specifies the data table using Db::table('sysdbuil') and adds alias('a') . leftJoin part retains the left join operation of the original code. The key is field('sum(a.jin) as jin_sum, sum(a.chu) as chu_sum') , which specifies the fields to be queried, and uses the sum() function to calculate the sum of the two columns jin and chu , and gives the result alias jin_sum and chu_sum to facilitate subsequent access. Finally, select() method executes the query and returns the result.

This method is equivalent to the original SQL statement function and can correctly return the sum result of the two columns jin and chu , avoiding the problem of returning only single column results in the original code. By using the combination of field() method and the sum() function, we can flexibly handle database aggregation queries in the ThinkPHP6 framework.

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