Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
2.0k views
in Technique[技术] by (71.8m points)

mysql - Count number of unique values

If I have three columns:

orderNumber, name, email

and I would like to count how many unique emails are in the table how would I go about doing so?

A statement like:

SELECT count(email) FROM orders

gives me the total count.

I tried SELECT DISTINCT count(email) FROM orders

but that does not seem to be giving me the numbers I am expecting.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

use

SELECT count( DISTINCT(email) ) FROM orders

Distinct provide unique email ids and then simply count them.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...