我就废话不多说了，大家还是直接看代码吧~

SELECT sum(aa) as "recordNumber" FROM table SELECT sum(aa) as recordNumber FROM table

postgis查询字段是将字段字段转为小写，如果需要大写的字符，需要加双引号

补充：Postgresql中表名、列名、用户名大小写问题

注意：是双引号，单引号可能会被解析成普通字符，因而是不识别的字段

highgo=# create table "ExChange" (id int);CREATE TABLEhighgo=# create table ExChange (id int);CREATE TABLEhighgo=# \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 1highgo=# 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 1highgo=# select * FROM "ExChange" ; id---- 2(1 row) highgo=# select * FROM exchange ; id---- 1 2(2 rows)

> 从上面可以看出，如果不加双引号，那么表名都会被转化为小写。如果想要大小写混用，需要添加双引号。

highgo=# create table exchange (ID int,id int);ERROR: 42701: column "id" specified more than oncehighgo=# create table exchange (ID int,name text);CREATE TABLEhighgo=# 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 existLINE 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 existshighgo=# create user "AAA";CREATE ROLEhighgo=# \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 | {}

实验证明，字段与用户同样会被自动转化为小写，除非添加双引号。 其实最好的办法就是全部用小写，这样才能尽量减少问题的出现。

以上为个人经验，希望能给大家一个参考，也希望大家多多支持。如有错误或未考虑完全的地方，望不吝赐教。