使用不同参数测试函数中的null

Question

我有一个Postgres功能:

create function myfunction(integer, text, text, text, text, text, text) RETURNS 
table(id int, match text, score int, nr int, nr_extra character varying, info character varying, postcode character varying,
street character varying, place character varying, country character varying, the_geom geometry)
AS $$
BEGIN

return query (select a.id, 'address' as match, 1 as score, a.ad_nr, a.ad_nr_extra,a.ad_info,a.ad_postcode, s.name as street, p.name place , c.name country, a.wkb_geometry as wkb_geometry from "Addresses" a 
    left join "Streets" s on a.street_id = s.id 
        left join "Places" p on s.place_id = p.id 
            left join "Countries" c on p.country_id = c.id 
            where c.name = $7 
                and p.name = $6
                    and s.name = $5
                    and a.ad_nr = $1 
                    and a.ad_nr_extra = $2
                    and a.ad_info = $3
                    and ad_postcode = $4);
END;
$$
LANGUAGE plpgsql;

当输入的一个或多个变量为NULL时,此函数无法给出正确的结果,因为ad_postcode = NULL它将失败.

我该怎么做才能在查询中测试NULL？

Answer 1

我不同意其他答案中的一些建议.这可以通过plpgsql完成,我认为它远远优于在客户端应用程序中组装查询.它更快更干净,应用程序只在请求中发送最小的线路.SQL语句保存在数据库中,这使得维护更容易 - 除非您想要在客户端应用程序中收集所有业务逻辑,这取决于一般体系结构.

一般建议

• 你不需要周围的括号SELECT用RETURN QUERY

• 切勿使用name和id作为列名.它们不具有描述性,当您加入一堆表(就像您必须a lot在关系数据库中)时,您最终会得到几个名为name或的列id.咄.

• 请至少在提出公开问题时正确格式化您的SQL.但为了你自己的利益,也要私下做.

PL/pgSQL函数

CREATE OR REPLACE FUNCTION func(
      _ad_nr       int  = NULL
    , _ad_nr_extra text = NULL
    , _ad_info     text = NULL
    , _ad_postcode text = NULL
    , _sname       text = NULL
    , _pname       text = NULL
    , _cname       text = NULL)
  RETURNS TABLE(id int, match text, score int, nr int, nr_extra text
              , info text, postcode text, street text, place text
              , country text, the_geom geometry) AS
$func$
BEGIN

-- RAISE NOTICE '%', -- for debugging
RETURN QUERY EXECUTE concat(
$$SELECT a.id, 'address'::text, 1 AS score, a.ad_nr, a.ad_nr_extra
     , a.ad_info, a.ad_postcode$$

, CASE WHEN (_sname, _pname, _cname) IS NULL THEN ', NULL::text' ELSE ', s.name' END  -- street
, CASE WHEN (_pname, _cname) IS NULL         THEN ', NULL::text' ELSE ', p.name' END  -- place
, CASE WHEN _cname IS NULL                   THEN ', NULL::text' ELSE ', c.name' END  -- country
, ', a.wkb_geometry'

, concat_ws('
JOIN   '
, '
FROM   "Addresses" a'
, CASE WHEN NOT (_sname, _pname, _cname) IS NULL THEN '"Streets"   s ON s.id = a.street_id' END
, CASE WHEN NOT (_pname, _cname) IS NULL         THEN '"Places"    p ON p.id = s.place_id' END
, CASE WHEN _cname IS NOT NULL                   THEN '"Countries" c ON c.id = p.country_id' END
)

, concat_ws('
AND    '
   , '
WHERE  TRUE'
   , CASE WHEN $1 IS NOT NULL THEN 'a.ad_nr = $1' END
   , CASE WHEN $2 IS NOT NULL THEN 'a.ad_nr_extra = $2' END
   , CASE WHEN $3 IS NOT NULL THEN 'a.ad_info = $3' END
   , CASE WHEN $4 IS NOT NULL THEN 'a.ad_postcode = $4' END
   , CASE WHEN $5 IS NOT NULL THEN 's.name = $5' END
   , CASE WHEN $6 IS NOT NULL THEN 'p.name = $6' END
   , CASE WHEN $7 IS NOT NULL THEN 'c.name = $7' END
)
)
USING $1, $2, $3, $4, $5, $6, $7;

END
$func$ LANGUAGE plpgsql;

呼叫:

SELECT * FROM func(1, '_ad_nr_extra', '_ad_info', '_ad_postcode', '_sname');

SELECT * FROM func(1, _pname := 'foo');

• 由于我为所有函数参数提供了默认值,因此您可以在函数调用中使用位置表示法,命名表示法或混合表示法.更多相关答案:
  具有可变数量输入参数的函数

• 有关动态SQL基础知识的更多说明,请参考以下相关答案:
  重构PL/pgSQL函数以返回各种SELECT查询的输出

• 该concat()函数有助于构建字符串.它与Postgres 9.1一起推出.

• 语句的ELSE分支CASE默认为NULL不存在时.简化代码.

• 这个USING子句EXECUTE使得SQL注入变得不可能,并且允许直接使用参数值,就像准备好的语句一样.

• NULL值用于忽略参数.它们实际上并不用于搜索.

简单的SQL函数

您可以使用纯SQL函数执行此操作并避免使用动态SQL.在某些情况下,这可能会更快.但在这种情况下我不会指望它.使用或不使用连接重新规划查询,以及条件是优越方法.它将为您提供优化的查询计划.像这样的简单查询的计划成本几乎可以忽略不计.

CREATE OR REPLACE FUNCTION func_sql(
     _ad_nr       int  = NULL
   , _ad_nr_extra text = NULL
   , _ad_info     text = NULL
   , _ad_postcode text = NULL
   , _sname       text = NULL
   , _pname       text = NULL
   , _cname       text = NULL)
  RETURNS TABLE(id int, match text, score int, nr int, nr_extra text
              , info text, postcode text, street text, place text
              , country text, the_geom geometry) AS 
$func$

SELECT a.id, 'address' AS match, 1 AS score, a.ad_nr, a.ad_nr_extra
     , a.ad_info, a.ad_postcode
     , s.name AS street, p.name AS place
     , c.name AS country, a.wkb_geometry
FROM   "Addresses"      a
LEFT   JOIN "Streets"   s ON s.id = a.street_id
LEFT   JOIN "Places"    p ON p.id = s.place_id
LEFT   JOIN "Countries" c ON c.id = p.country_id
WHERE ($1 IS NULL OR a.ad_nr = $1)
AND   ($2 IS NULL OR a.ad_nr_extra = $2)
AND   ($3 IS NULL OR a.ad_info = $3)
AND   ($4 IS NULL OR a.ad_postcode = $4)
AND   ($5 IS NULL OR s.name = $5)
AND   ($6 IS NULL OR p.name = $6)
AND   ($7 IS NULL OR c.name = $7)

$func$ LANGUAGE sql;

相同的电话.

要有效地忽略带有NULL值的参数:

($1 IS NULL OR a.ad_nr = $1)

如果您确实想使用NULL值作为参数,请改用此构造:

($1 IS NULL AND a.ad_nr IS NULL OR a.ad_nr = $1)  -- AND binds before OR

这也允许使用索引.
同时更换的所有实例LEFT JOIN有JOIN.

SQL Fiddle与所有变体的简化演示.