如何在 PostgreSQL 中测试 if 语句？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/9151863/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
How to test an if statement in PostgreSQL?
提问by Stefan Steiger
Question: I want to test an if statement in PostgreSQL:
问题：我想在 PostgreSQL 中测试一个 if 语句：
IF (SELECT COUNT(*) FROM pg_language WHERE lanname = 'plpgsql') > 0 THEN
PRINT 'Good'
ELSE
PRINT 'Bad'
END IF;
Now this throws an error at IF.
现在这会在 IF 处引发错误。
As far as I have read, this is because I need to use plpgsql to be able to use if, print, and variables.
据我所知，这是因为我需要使用 plpgsql 才能使用 if、print 和 variables。
So far, I probably also have to use SELECT instead of print as well.
到目前为止，我可能还必须使用 SELECT 而不是打印。
How can I switch the language before executing this statement to plpgsql ?
如何在执行此语句到 plpgsql 之前切换语言？
I want to test it first, BEFORE I put it in a stored procedure. To test code with variables etc.
我想先对其进行测试，然后再将其放入存储过程。用变量等测试代码。
Edit:
Solved by:
编辑：
解决：
DO LANGUAGE plpgsql $$
BEGIN
IF (SELECT COUNT(*) FROM pg_language WHERE lanname = 'plpgsql') > 0 THEN
RAISE NOTICE 'GOOD';
ELSE
RAISE NOTICE 'BAD';
END IF;
END;
$$;
回答by mu is too short
If you just want to test code snippets without going through all the hassle of building and dropping a function, then you can use DO:
如果您只想测试代码片段而不经历构建和删除函数的所有麻烦，那么您可以使用DO：
=> do language plpgsql $$
begin
-- Yes, I have a table called pancakes in my playpen database.
if (select count(*) from pancakes) > 0 then
raise notice 'Got some';
else
raise notice 'Got none';
end if;
end;
$$;
You'll need 9.0+ to use DO.
您需要 9.0+ 才能使用DO.
