sql query if parameter is null select all

Try this:

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

You can also use functions IFNULL,COALESCE,NVL,ISNULL to check null value. It depends on your RDBMS.

MySQL:

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

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);

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