域名預(yù)訂/競(jìng)價(jià)，好“米”不錯(cuò)過(guò)

這篇文章主要介紹了postgresql查詢自動(dòng)將大寫(xiě)的名稱轉(zhuǎn)換為小寫(xiě)的案例，具有很好的參考價(jià)值，希望對(duì)大家有所幫助。一起跟隨小編過(guò)來(lái)看看吧

我就廢話不多說(shuō)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(xiě)，如果需要大寫(xiě)的字符，需要加雙引號(hào)

補(bǔ)充：Postgresql中表名、列名、用戶名大小寫(xiě)問(wèn)題

注意：是雙引號(hào)，單引號(hào)可能會(huì)被解析成普通字符，因而是不識(shí)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(hào)，那么表名都會(huì)被轉(zhuǎn)化為小寫(xiě)。如果想要大小寫(xiě)混用，需要添加雙引號(hào)。

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(shí)驗(yàn)證明，字段與用戶同樣會(huì)被自動(dòng)轉(zhuǎn)化為小寫(xiě)，除非添加雙引號(hào)。 其實(shí)最好的辦法就是全部用小寫(xiě)，這樣才能盡量減少問(wèn)題的出現(xiàn)。

文章來(lái)源：腳本之家

來(lái)源地址：https://www.jb51.net/article/204960.htm

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