Tagged Questions

1
vote
1answer
36 views

How can I make a select statement get blocked?

Hello I am trying to intentionally make a SQL select statement get blocked by another simple SQL delete or update statement, for the purpose of learning. I prefer only InnoDB tables. To prepare the ...
1
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1answer
86 views

select count(*) in mysql 5.5 innodb— rewrite advice?

I need advice on how to rewrite a select count(*) query for innodb tables mysql 5.5. in new environment its very slow... select count(*) from mails3 join questions using (question_id) where ...
1
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2answers
114 views

Is it always bad to use SELECT * FROM?

It is widely recommended NOT to use SELECT *. I understand this, as it is not a good idea to bring the entire row into memory, when only a few cells are needed. Is it still bad to use SELECT * when ...
2
votes
2answers
998 views

How do I get the current and next greater value in one select?

I have a InnoDB table 'idtimes' (MySQL 5.0.22-log) with columns `id` int(11) NOT NULL, `time` int(20) NOT NULL, [...] with a compound unique key UNIQUE KEY `id_time` (`id`,`time`) so there can ...
1
vote
1answer
341 views

How to change the display of an empty string in mysql command line tool?

I'm maintaining a database with InnoDB tables. These tables have some columns of type (from show create table): `val0` varchar(30) default NULL, `val1` varchar(30) default NULL, etc... From the ...
3
votes
2answers
281 views

Should I use select count(*) for counting records or having a field like comments_no for tables like post, comments?

In my recent project which is about social networking for an Asian country, I'm in doubt whether I use the below SQL statement for counting records: SELECT COUNT(id) shareLikeNo FROM ...