尝试：

Try:

SELECT * FROM table WHERE date=@date AND (@abc IS NULL OR abc=@abc)

你应该检查这样一个条件你的代码并执行一个不同的查询，即

You should check such a a condition in your code and execute a different query, namely

select * from table where date=@date

用于忽略'empty' abc 参数。

您可以使用if ... else ...条件来检查它是否有数据。

You can use if...else... condition to check whether it is having data or not.

if @date and @abc is not null
begin
    "Your select statement" Where date=@date and abc=@abc
end
if @date is not null and @abc is null
begin
    "Your select statement" Where date=@date 
end
if @date is null and @abc is not null
begin
    "Your select statement" Where abc=@abc
end