如果满足条件，则插入 [英] INSERT INTO if condition is satisfied

问题描述

仅当$solution[$i][0]属于查询SELECT num_arr FROM Schedule WHERE num_arr<>''的结果时，才需要将数组$solution保存到SQL表中.如果它不属于它，则必须不将行$ i保存在SQL表中.以下提供的查询似乎不正确.如何执行所描述的任务?正确的方法是什么?

I need to save the array $solution into the SQL table only if $solution[$i][0] belongs to the result of the query SELECT num_arr FROM Schedule WHERE num_arr<>''. If it does not belong to it, then the row $i must be not saved in the SQL table. The below-provided query seems to be incorrect. How do I implement the described task? What would be the correct approach to do this?

$query_land = "INSERT INTO `Sequence` (`num_arr`,`start`,`fin`,`way_id`) 
               VALUES ('".$solution[$i][0]."','".$solution[$i][1]."',
                                   '".$solution[$i][2]."','".$solution[$i][3]."') 
               WHERE '".$solution[$i][0]."' IN (SELECT num_arr 
                                                FROM Schedule 
                                                WHERE num_arr<>'')";

推荐答案

INSERT陈述有两个变体:

INSERT INTO tableX
    (a, b, c, ...)
VALUES
    (1, 2, 3, ...) ;

和

INSERT INTO tableX
    (a, b, c, ...)
SELECT
    1, 2, 3
FROM
    ... ;             --- the same or another table or many tables

dual是仅具有1行的系统表.它可以用于各种事物.在这里使用它是为了将VALUES (...)重写为SELECT ...，在该位置我们没有任何合适的表可放在FROM子句中:

The dual is a system table with exactly 1 row. It can be used for various things. Here it's used so a VALUES (...) is rewritten as a SELECT ... where we don't have any suitable table to put in the FROM clause:

$query_land = "INSERT INTO `Sequence` (`num_arr`,`start`,`fin`,`way_id`) 
               SELECT '".$solution[$i][0]."','".$solution[$i][1]."',
                      '".$solution[$i][2]."','".$solution[$i][3]."'
               FROM dual 
               WHERE '".$solution[$i][0]."' IN (SELECT num_arr 
                                                FROM Schedule 
                                                WHERE num_arr<>'')";

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