php – 如果子查询的结果为NULL,则整个查询失败

发布时间：2020-12-13 18:10:19 所属栏目：PHP教程来源：网络整理

导读：我有一种情况,我需要从同一个表的有效数据中生成包含随机数据的行我通过php rand($min,$max)函数生成ID,$min = 1,$max = [SELECT MAX(ID)FROM patient] – 1 SelecttblFirstName.FirstName,tblLastName.LastName,tblBirthDate.BirthDate,tblLocation.Locati

我有一种情况,我需要从同一个表的有效数据中生成包含随机数据的行

我通过php rand($min,$max)函数生成ID,$min = 1,$max = [SELECT MAX(ID)FROM patient] – 1

Select

tblFirstName.FirstName,tblLastName.LastName,tblBirthDate.BirthDate,tblLocation.Location

From

(SELECT FirstName FROM patient WHERE ID > 11445 AND FirstName != '' LIMIT 1) AS tblFirstName,(SELECT LastName FROM patient WHERE ID > 74964 AND LastName != '' LIMIT 1) AS tblLastName,(SELECT BirthDate FROM patient WHERE ID > 26360 LIMIT 1) AS tblBirthDate,(SELECT Location FROM patient WHERE ID > 68356 AND Location != '' LIMIT 1) AS tblLocation

现在在ID>从上述查询26360得到的26360是随机数>用于避免26360被删除的可能性

问题：

如果任何子查询返回没有结果,则完成查询失败并且不返回任何内容.

试试这个：

SELECT (SELECT FirstName FROM patient WHERE ID > 11445 AND FirstName != '' LIMIT 1) AS tblFirstName,(SELECT Location FROM patient WHERE ID > 68356 AND Location != '' LIMIT 1) AS tblLocation

（编辑：李大同）

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