Question

请参阅本说明末尾的重要新发现1和2.

我正在运行Postgres 9.1.3并且有一个奇怪的左连接问题。

我有一个名为 consistent.master 的表格，行数超过200万。它有一个名为 citation_id 的列，该列没有空值。我可以用这个验证：

SELECT COUNT(*)
FROM consistent.master
WHERE citation_id IS NULL

返回 0 。

这里有点奇怪：如果我 LEFT JOIN 这个表到临时表，我得到一个错误，我试图在 citation_id 字段中插入一个null ：

错误：“citation_id”列中的空值违反了非空约束 SQL状态：23502

以下是查询：

WITH stops AS (
    SELECT citation_id,
           rank() OVER (ORDER BY offense_timestamp,
                     defendant_dl,
                     offense_street_number,
                     offense_street_name) AS stop
    FROM   consistent.master
    WHERE  citing_jurisdiction=1
)

INSERT INTO consistent.masternew (arrest_id, citation_id, defendant_dl, defendant_dl_state, defendant_zip, defendant_race, defendant_sex, defendant_dob, vehicle_licenseplate, vehicle_licenseplate_state, vehicle_registration_expiration_date, vehicle_year, vehicle_make, vehicle_model, vehicle_color, offense_timestamp, offense_street_number, offense_street_name, offense_crossstreet_number, offense_crossstreet_name, offense_county, officer_id, offense_code, speed_alleged, speed_limit, work_zone, school_zone, offense_location, id, source, citing_jurisdiction, the_geom)

SELECT stops.stop, master.citation_id, defendant_dl, defendant_dl_state, defendant_zip, defendant_race, defendant_sex, defendant_dob, vehicle_licenseplate, vehicle_licenseplate_state, vehicle_registration_expiration_date, vehicle_year, vehicle_make, vehicle_model, vehicle_color, offense_timestamp, offense_street_number, offense_street_name, offense_crossstreet_number, offense_crossstreet_name, offense_county, officer_id, offense_code, speed_alleged, speed_limit, work_zone, school_zone, offense_location, id, source, citing_jurisdiction, the_geom
FROM consistent.master LEFT JOIN stops
ON stops.citation_id = master.citation_id

我在这个问题上摸不着头脑。如果这是 LEFT JOIN ，并且 consistent.master 是联接的左表，则此查询如何在 citation_id 列中创建空值什么时候开始没有？

这是我用来创建表的SQL代码：

CREATE TABLE consistent.masternew
(
  arrest_id character varying(20),
  citation_id character varying(20) NOT NULL,
  defendant_dl character varying(20),
  defendant_dl_state character varying(2),
  defendant_zip character varying(9),
  defendant_race character varying(10),
  defendant_sex character(1),
  defendant_dob date,
  vehicle_licenseplate character varying(10),
  vehicle_licenseplate_state character(2),
  vehicle_registration_expiration_date date,
  vehicle_year integer,
  vehicle_make character varying(20),
  vehicle_model character varying(20),
  vehicle_color character varying,
  offense_timestamp timestamp without time zone,
  offense_street_number character varying(10),
  offense_street_name character varying(30),
  offense_crossstreet_number character varying(10),
  offense_crossstreet_name character varying(30),
  offense_county character varying(10),
  officer_id character varying(20),
  offense_code integer,
  speed_alleged integer,
  speed_limit integer,
  work_zone bit(1),
  school_zone bit(1),
  offense_location point,
  id serial NOT NULL,
  source character varying(20), -- Where this citation came from--court, PD, etc.
  citing_jurisdiction integer,
  the_geom geometry,
  CONSTRAINT masternew_pkey PRIMARY KEY (id ),
  CONSTRAINT citing_jurisdiction FOREIGN KEY (citing_jurisdiction)
      REFERENCES consistent.jurisdictions (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT offenses FOREIGN KEY (offense_code)
      REFERENCES consistent.offenses (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION,
  CONSTRAINT enforce_dims_the_geom CHECK (st_ndims(the_geom) = 2),
  CONSTRAINT enforce_geotype_the_geom CHECK (geometrytype(the_geom) = 'POINT'::text OR the_geom IS NULL),
  CONSTRAINT enforce_srid_the_geom CHECK (st_srid(the_geom) = 3081)
)
WITH (
  OIDS=FALSE
);
ALTER TABLE consistent.masternew
  OWNER TO postgres;
COMMENT ON COLUMN consistent.masternew.source IS 'Where this citation came from--court, PD, etc.';

CREATE INDEX masternew_citation_id_idx
  ON consistent.masternew
  USING btree
  (citation_id COLLATE pg_catalog."default" );

CREATE INDEX masternew_citing_jurisdiction_idx
  ON consistent.masternew
  USING btree
  (citing_jurisdiction );

CREATE INDEX masternew_defendant_dl_idx
  ON consistent.masternew
  USING btree
  (defendant_dl COLLATE pg_catalog."default" );

CREATE INDEX masternew_id_idx
  ON consistent.masternew
  USING btree
  (id );

CREATE INDEX masternew_offense_street_name_idx
  ON consistent.masternew
  USING btree
  (offense_street_name COLLATE pg_catalog."default" );

CREATE INDEX masternew_offense_street_number_idx
  ON consistent.masternew
  USING btree
  (offense_street_number COLLATE pg_catalog."default" );

CREATE INDEX masternew_offense_timestamp_idx
  ON consistent.masternew
  USING btree
  (offense_timestamp );

CREATE INDEX masternew_the_geom_idx
  ON consistent.masternew
  USING gist
  (the_geom );

重要发现1

我刚刚发现了一些有趣的东西。这个查询：

SELECT COUNT(*)
FROM consistent.master
WHERE citation_id IS NOT NULL
UNION
SELECT COUNT(*)
FROM consistent.master
UNION
SELECT COUNT(*)
FROM consistent.master
WHERE citation_id IS NULL

结果是：

2085344
2085343
0

我怎么能解释这个？ WHERE citation_id IS NOT NULL的计数如何可能高于没有WHERE子句的同一查询？

重要发现2 好的，根据下面的评论，我发现我有一行包含所有空值，这是尽管这个表有一个串行id列和一些{{1}约束。

我删除了屁股行。现在我没有得到null错误。相反，我得到了这个：

NOT NULL

所以只是为了确保，我做了这个查询：

ERROR:  duplicate key value violates unique constraint "masternew_pkey"
DETAIL:  Key (id)=(1583804) already exists.

********** Error **********

ERROR: duplicate key value violates unique constraint "masternew_pkey"
SQL state: 23505
Detail: Key (id)=(1583804) already exists.

猜猜是什么？

SELECT COUNT(id)
FROM consistent.master
WHERE id=1583804;

只有1个这样的实例！因此，consistent.master只有LEFT JOIN 1583804 <{1>} 中的左侧表格 列中的左侧表格 id 只能来自左表，这个错误怎么可能发生？这样的citation_id不应该导致最终结果的行数多于左表，对吗？

Answer 1

使用INSERT，尤其是复杂的INSERT，您应该始终定义目标列。所以说：

INSERT INTO consistent.masternew (citation_id, col1, col2, ...)

如果随附的SELECT语句出现任何问题 - 就像这样：

the_geom geometry

（使用类型名称重命名列是没有意义的 - 我认为这是无意的） - 或者如果基础表定义发生更改，则没有定义目标列的INSERT语句可能会出现严重错误。

PostgreSQL不会在SELECT语句中强制执行与目标表中相同数量的列。我引用the fine manual on that：

显式或隐式列列表中不存在的每个列都将填充默认值，或者声明默认值或如果没有，则为null 。

（大胆强调我的。）如果列列表中存在不匹配，则可能会使“无处不在”的NULL值出现。

此外，SELECT语句中列的顺序必须与要插入的列的顺序相匹配。如果目标列没有拼写出来，那么这将是表格中创建的列的顺序您似乎希望列自动匹配名称，但事实并非如此。 SELECT语句中的列名与INSERT的最后一步完全无关。只有他们从左到右的顺序才是重要的。

与其他人所暗示的相反， WITH子句完全合法。我引用the manual on INSERT：

查询（SELECT语句）也可以包含WITH 条款。在这种情况下，可以引用两组with_query 在查询中，但第二个优先，因为它更多紧密嵌套。

您的陈述可能如下所示：

WITH stops AS (
    SELECT citation_id
          ,rank() OVER (ORDER BY
                    offense_timestamp
                   ,defendant_dl
                   ,offense_street_number
                   ,offense_street_name) AS stop
    FROM   consistent.master
    WHERE  citing_jurisdiction = 1
    )
INSERT INTO consistent.masternew (citation_id, col1, col2, ...) -- add columns
SELECT m.citation_id -- order colums accordingly!
      ,s.stop
      ,m.defendant_dl
        -- 27 more columns
      ,m.citing_jurisdiction
      ,m.the_geom
FROM   consistent.master m
LEFT   JOIN stops s USING (citation_id);

Answer 2

猜测我会说你在citation_id列中插入了stops.stop，它可能是null，但是在不知道表结构的情况下我无法确定：）

编辑：尝试@ vol7ron的建议并命名列......

PostgreSQL：LEFT JOIN创建空白行

2 个答案: