PL/pgSQL中的變量替換

Question

我有一個基於提供的參數動態生成的select語句。問題是，postgresql總是說：

argument of WHERE must be type boolean, not type character varying不管參數是什麼。我錯過了什麼嗎？

CREATE OR REPLACE FUNCTION getuid(name character varying) RETURNS integer AS $$ 
    DECLARE 
     statement varchar; 
     uid integer; 
    BEGIN 
     IF ($1 = '') THEN 
      statement := 'TRUE'; 
      statement := CAST(statement AS BOOLEAN); 
     ELSE 
      statement := 'users.keywords ILIKE''' || '%' || $1 || '%'''; 
     END IF; 
     SELECT INTO uid id FROM users WHERE "statement"; 
     RETURN uid; 
    END; 
$$ LANGUAGE plpgsql 

Answer 1

EXECUTE是一個PL/pgSQL的聲明，而不是SQL語句。所以你必須將你的動態查詢包裝到PL/pgSQL存儲過程中。

小心變量替換，在構建查詢時不要忘記使用quote_literal()或quote_nullable()。

已在此處查看文檔：http://www.postgresql.org/docs/current/static/plpgsql-statements.html#PLPGSQL-STATEMENTS-EXECUTING-DYN

Answer 2

如果要在函數內部生成動態命令，則需要EXECUTE。你也可以使用兩個不同的部分：

CREATE OR REPLACE FUNCTION getuid(name character varying) RETURNS integer AS $$ 
    DECLARE 
     statement varchar; 
     uid integer; 
    BEGIN 
     IF ($1 = '' OR $1 IS NULL) THEN -- section 1 
      SELECT id INTO uid FROM users; 
     ELSE -- section 2 
      SELECT id INTO uid FROM users WHERE users.keywords ILIKE '%' || $1 || '%'; 
     END IF; 

     RETURN uid; 
    END; 
$$ LANGUAGE plpgsql;