n*u
2 楼
Sorry to bother high hands again. Thanks for your help before!
Table a, articleid (pk), userid, datetime, textbody
Table b, userid (pk), nickname
I want one record, that's the latest article, with nickname, datetime and
textbody.
So I wrote this:
SELECT a.DateTime,b.Nickname,a.textbody
FROM a, b
WHERE a.userid=b.userid
ORDER BY datatime DESC
LIMIT 0, 1
But I feel this might be slow. Any way to make it fast?
I told my team leader we should write this as a stored procedure, but he
refused.
Table a, articleid (pk), userid, datetime, textbody
Table b, userid (pk), nickname
I want one record, that's the latest article, with nickname, datetime and
textbody.
So I wrote this:
SELECT a.DateTime,b.Nickname,a.textbody
FROM a, b
WHERE a.userid=b.userid
ORDER BY datatime DESC
LIMIT 0, 1
But I feel this might be slow. Any way to make it fast?
I told my team leader we should write this as a stored procedure, but he
refused.
q*x
3 楼
赞！
背景那个四个圈圈是纸的装饰，还是用来方便控制字体大小的啊？
背景那个四个圈圈是纸的装饰，还是用来方便控制字体大小的啊？
c*d
4 楼
1. create index on table_a (datetime)
2. select ... from a, b where a.userid=b.userid and a.datetime=(select max(d
atetime) from a
【在 n****u 的大作中提到】
: Sorry to bother high hands again. Thanks for your help before!
: Table a, articleid (pk), userid, datetime, textbody
: Table b, userid (pk), nickname
: I want one record, that's the latest article, with nickname, datetime and
: textbody.
: So I wrote this:
: SELECT a.DateTime,b.Nickname,a.textbody
: FROM a, b
: WHERE a.userid=b.userid
: ORDER BY datatime DESC
2. select ... from a, b where a.userid=b.userid and a.datetime=(select max(d
atetime) from a
【在 n****u 的大作中提到】
: Sorry to bother high hands again. Thanks for your help before!
: Table a, articleid (pk), userid, datetime, textbody
: Table b, userid (pk), nickname
: I want one record, that's the latest article, with nickname, datetime and
: textbody.
: So I wrote this:
: SELECT a.DateTime,b.Nickname,a.textbody
: FROM a, b
: WHERE a.userid=b.userid
: ORDER BY datatime DESC
p*3
5 楼
谢谢MM，内行啊, 您说的很对。背景那个四个圈圈是纸的装饰, 同时又是用来方便控制
字体大小.
【在 q**x 的大作中提到】
: 赞！
: 背景那个四个圈圈是纸的装饰，还是用来方便控制字体大小的啊？
字体大小.
【在 q**x 的大作中提到】
: 赞！
: 背景那个四个圈圈是纸的装饰，还是用来方便控制字体大小的啊？
n*6
6 楼
未经测试。
SELECT a.articleid, ...., max(a.datetime), ...
FROM a, b
WHERE a.userid = b.userid
【在 n****u 的大作中提到】
: Sorry to bother high hands again. Thanks for your help before!
: Table a, articleid (pk), userid, datetime, textbody
: Table b, userid (pk), nickname
: I want one record, that's the latest article, with nickname, datetime and
: textbody.
: So I wrote this:
: SELECT a.DateTime,b.Nickname,a.textbody
: FROM a, b
: WHERE a.userid=b.userid
: ORDER BY datatime DESC
SELECT a.articleid, ...., max(a.datetime), ...
FROM a, b
WHERE a.userid = b.userid
【在 n****u 的大作中提到】
: Sorry to bother high hands again. Thanks for your help before!
: Table a, articleid (pk), userid, datetime, textbody
: Table b, userid (pk), nickname
: I want one record, that's the latest article, with nickname, datetime and
: textbody.
: So I wrote this:
: SELECT a.DateTime,b.Nickname,a.textbody
: FROM a, b
: WHERE a.userid=b.userid
: ORDER BY datatime DESC
f*n
7 楼
我更喜欢左边的题字，嘻嘻
c*d
8 楼
your solution only works when "select max(a.datetime)"
in his case, he needs more than 1 column with aggregate columns
【在 n********6 的大作中提到】
: 未经测试。
: SELECT a.articleid, ...., max(a.datetime), ...
: FROM a, b
: WHERE a.userid = b.userid
in his case, he needs more than 1 column with aggregate columns
【在 n********6 的大作中提到】
: 未经测试。
: SELECT a.articleid, ...., max(a.datetime), ...
: FROM a, b
: WHERE a.userid = b.userid
n*u
9 楼
Thanks, it did improve the query speed. Cut off time more than 50%!
B*g
10 楼
回贴没原文. what is "it"?
【在 n****u 的大作中提到】
: Thanks, it did improve the query speed. Cut off time more than 50%!
【在 n****u 的大作中提到】
: Thanks, it did improve the query speed. Cut off time more than 50%!
c*d
11 楼
肯定是我那个
另外一个语法就不work
【在 B*****g 的大作中提到】
: 回贴没原文. what is "it"?
另外一个语法就不work
【在 B*****g 的大作中提到】
: 回贴没原文. what is "it"?
n*u
12 楼
using max(datetime), hehe
【在 B*****g 的大作中提到】
: 回贴没原文. what is "it"?
【在 B*****g 的大作中提到】
: 回贴没原文. what is "it"?
c*d
13 楼
两个都用了max(datetime)
【在 n****u 的大作中提到】
: using max(datetime), hehe
【在 n****u 的大作中提到】
: using max(datetime), hehe
B*g
14 楼
其实我想问有没有create index。
【在 c*****d 的大作中提到】
: 肯定是我那个
: 另外一个语法就不work
【在 c*****d 的大作中提到】
: 肯定是我那个
: 另外一个语法就不work
n*u
15 楼
Thanks! The query really speeds up a lot!
【在 c*****d 的大作中提到】
: 肯定是我那个
: 另外一个语法就不work
【在 c*****d 的大作中提到】
: 肯定是我那个
: 另外一个语法就不work
n*u
16 楼
I tried his code w/o creating index. it's fast
but after I created index, it's slow.
【在 B*****g 的大作中提到】
: 其实我想问有没有create index。
but after I created index, it's slow.
【在 B*****g 的大作中提到】
: 其实我想问有没有create index。
B*g
17 楼
hehe.
【在 n****u 的大作中提到】
: I tried his code w/o creating index. it's fast
: but after I created index, it's slow.
【在 n****u 的大作中提到】
: I tried his code w/o creating index. it's fast
: but after I created index, it's slow.
c*d
18 楼
嗯,为什么这样,不make sense呀?
【在 B*****g 的大作中提到】
: hehe.
【在 B*****g 的大作中提到】
: hehe.
n*u
19 楼
I will take a look at that. Maybe I mess up something... hehe
【在 c*****d 的大作中提到】
: 嗯,为什么这样,不make sense呀?
【在 c*****d 的大作中提到】
: 嗯,为什么这样,不make sense呀?
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