sql - Oracle SQL 技巧

Question

我想在 SQL 查询的 where 子句中的 oracle SQL 中执行以下操作

$p="All" 然后 buildingname in(Select buildingname from Building) else buildingname="$p"

问题是我无法解析这个 $p 变量，即我无法检查它包含的内容

Answer 1

听起来你只是想要一个OR条件，

SELECT *
  FROM sometable
 WHERE (    :bind_variable = 'All' 
        AND buildingname IN (SELECT buildingname
                              FROM building))
     OR buildingname = :bind_variable

Answer 2

您可以在子查询中使用 OR，因此如果 $p 是“全部”，它要么选择建筑物选择，要么选择全部

buildingname in (Select buildingname from Building WHERE buildingname = $p OR $p = 'All')

Answer 3

如果字符串中的变量被它包含的任何内容替换（因此它不是绑定变量，而只是来自 PERL 或 PHP 等语言的变量，并在您正在构建的选择字符串中使用）：

$selectstring = "SELECT *
  FROM sometable
 WHERE (    '$p' = 'All' 
        AND buildingname IN (SELECT buildingname
                              FROM building))
     OR (   '$p' <> 'All' AND buildingname = '$p'"

意识到 SQL 注入的危险。绑定变量更好。无论如何，包含值“All”的变量 $p 的语句将是

SELECT *
  FROM sometable
 WHERE (    'All' = 'All' 
        AND buildingname IN (SELECT buildingname
                              FROM building))
     OR (   'All' <> 'All' AND buildingname = 'All')

虽然您将有一个变量 $p 的选择字符串，其中包含 'XYZ'

SELECT *
  FROM sometable
 WHERE (    'XYZ' = 'All' 
        AND buildingname IN (SELECT buildingname
                              FROM building))
     OR (   'XYZ' <> 'All' AND buildingname = 'XYZ')

但老实说，你也可以做类似的事情

if ($p eq 'All') {
...   one select
} else {
...   another select
}