SELECT
分析语句语法
完整的分析语句语法如下:
1 2 3 4 |
SELECT [DISTINCT] (* | expression) [AS alias] [, ...] [GROUP BY expression [, ...] [HAVING predicates]] [ORDER BY expression [ASC | DESC] [, ...]] [LIMIT size OFFSET offset] |
其中,SELECT表示指定查询的字段。本章节内容将介绍SELECT语法参数说明及示例。
使用*查询所有字段
1
|
SELECT * |
|
account_number |
firstname |
gender |
city |
balance |
employer |
state |
lastname |
age |
|---|---|---|---|---|---|---|---|---|
|
1 |
Amber |
M |
Brogan |
39225 |
Pyrami |
IL |
Duke |
32 |
|
16 |
Hattie |
M |
Dante |
5686 |
Netagy |
TN |
Bond |
36 |
|
13 |
Nanette |
F |
Nogal |
32838 |
Quility |
VA |
Bates |
28 |
|
18 |
Dale |
M |
Orick |
4180 |
null |
MD |
Adams |
32 |
查询指定字段
1
|
SELECT firstname, lastname |
|
firstname |
lastname |
|---|---|
|
Amber |
Duke |
|
Hattie |
Bond |
|
Nanette |
Bates |
|
Dale |
Adams |
使用AS给字段定义别名
1
|
SELECT account_number AS num |
|
num |
|---|
|
1 |
|
16 |
|
13 |
|
18 |
使用DISTINCT去重
1
|
SELECT DISTINCT age |
|
age |
|---|
|
32 |
|
36 |
|
28 |
使用SQL函数
函数相关内容请参见函数。
1
|
SELECT LENGTH(firstname) as len, firstname |
|
len |
firstname |
|---|---|
|
4 |
Amber |
|
6 |
Hattie |
|
7 |
Nanette |
|
4 |
Dale |