sql查询如果参数为null则选择全部

Question

我有以下查询:

SELECT NAME, SURNAME FROM MY_TABLE WHERE NAME = ?;

现在我想要那个'？' 为NULL,必须选择所有记录.我怎样才能在SQL中实现这一点？谢谢

Answer 1

试试这个:

SELECT * 
FROM MY_TABLE 
WHERE @parameter IS NULL OR NAME = @parameter;

Answer 2

您还可以使用的功能IFNULL,COALESCE,NVL,ISNULL检查空值.这取决于您的RDBMS.

MySQL:

SELECT NAME, SURNAME FROM MY_TABLE WHERE NAME = IFNULL(?,NAME);

要么

SELECT NAME, SURNAME FROM MY_TABLE WHERE NAME = COALESCE(?,NAME);

ORACLE:

SELECT NAME, SURNAME FROM MY_TABLE WHERE NAME = NVL(?,NAME);

SQL Server/SYBASE:

SELECT NAME, SURNAME FROM MY_TABLE WHERE NAME = ISNULL(?,NAME);