我就廢話不多說了，大家還是直接看代碼吧~
SELECT sum(aa) as "recordNumber" FROM table
SELECT sum(aa) as recordNumber FROM table
postgis查詢字段是將字段字段轉(zhuǎn)為小寫，如果需要大寫的字符，需要加雙引號
補充：Postgresql中表名、列名、用戶名大小寫問題
注意：是雙引號，單引號可能會被解析成普通字符，因而是不識別的字段
highgo=# create table "ExChange" (id int);
CREATE TABLE
highgo=# create table ExChange (id int);
CREATE TABLE
highgo=# \d
List of relations
Schema | Name | Type | Owner
----------------+----------+-------+--------
oracle_catalog | dual | view | highgo
public | ExChange | table | highgo
public | exchange | table | highgo
public | myt | table | highgo
public | t1 | table | highgo
public | tran | table | highgo
(6 rows)
highgo=# insert into exchange values (1);
INSERT 0 1
highgo=# insert into "ExChange" values (2);
INSERT 0 1
highgo=# select * FROM exchange ;
id
----
1
(1 row)
highgo=# select * FROM ExChange ;
id
----
1
(1 row)
highgo=# select * FROM "ExChange" ;
id
----
2
(1 row)
highgo=# insert into ExChange values (2);
INSERT 0 1
highgo=# select * FROM "ExChange" ;
id
----
2
(1 row)
highgo=# select * FROM exchange ;
id
----
1
2
(2 rows)
> 從上面可以看出，如果不加雙引號，那么表名都會被轉(zhuǎn)化為小寫。如果想要大小寫混用，需要添加雙引號。
highgo=# create table exchange (ID int,id int);
ERROR: 42701: column "id" specified more than once
highgo=# create table exchange (ID int,name text);
CREATE TABLE
highgo=# select id from exchange ;
id
----
(0 rows)
highgo=# select ID from exchange ;
id
----
(0 rows)
highgo=# select "ID" from exchange ;
ERROR: 42703: column "ID" does not exist
LINE 1: select "ID" from exchange ;
highgo=# \d exchange
Table "public.exchange"
Column | Type | Modifiers
--------+---------+-----------
id | integer |
name | text |
highgo=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------------------+-----------
aaa | | {}
gpadmin | Superuser, Create role, Create DB | {}
highgo | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
replica | Replication | {}
highgo=# create table AAA;
ERROR: 42601: syntax error at or near ";"
LINE 1: create table AAA;
^
highgo=# create user AAA;
ERROR: 42710: role "aaa" already exists
highgo=# create user "AAA";
CREATE ROLE
highgo=# \du
List of roles
Role name | Attributes | Member of
-----------+------------------------------------------------------------+-----------
AAA | | {}
aaa | | {}
gpadmin | Superuser, Create role, Create DB | {}
highgo | Superuser, Create role, Create DB, Replication, Bypass RLS | {}
replica | Replication | {}
實驗證明，字段與用戶同樣會被自動轉(zhuǎn)化為小寫，除非添加雙引號。 其實最好的辦法就是全部用小寫，這樣才能盡量減少問題的出現(xiàn)。
以上為個人經(jīng)驗，希望能給大家一個參考，也希望大家多多支持腳本之家。如有錯誤或未考慮完全的地方，望不吝賜教。
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