having

Does MySQL eliminate common subexpressions between SELECT and HAVING/GROUP BY clause

由 大兔子大兔子 提交于 2019-11-26 18:20:41
问题 I often see people answer MySQL questions with queries like this: SELECT DAY(date), other columns FROM table GROUP BY DAY(date); SELECT somecolumn, COUNT(*) FROM table HAVING COUNT(*) > 1; I always like to give the column an alias and refer to that in the GROUP BY or HAVING clause, e.g. SELECT DAY(date) AS day, other columns FROM table GROUP BY day; SELECT somecolumn, COUNT(*) AS c FROM table HAVING c > 1; Is MySQL smart enough to notice that the expressions in the later clauses are the same

Mysql: how to select groups having certain values?

由 别说谁变了你拦得住时间么 提交于 2019-11-26 17:33:40
问题 Say there is such table: mysql> SELECT * FROM tags; +---------+--------+ | post_id | tag_id | +---------+--------+ | 1 | 2 | | 1 | 3 | | 1 | 1 | | 2 | 1 | | 2 | 2 | +---------+--------+ 5 rows in set (0.00 sec) Field names are pretty self-explanatory. I want to select post_id s that have both 1 and 3 tag_id s, so in this example it's only 1 . I thought of something like SELECT post_id FROM tags GROUP BY post_id HAVING ... After having I'd like to list tag_id s that are present in this group.

SQL query for finding records where count > 1

由 亡梦爱人 提交于 2019-11-26 15:03:59
I have a table named PAYMENT . Within this table I have a user ID, an account number, a ZIP code and a date. I would like to find all records for all users that have more than one payment per day with the same account number. UPDATE: Additionally, there should be a filter than only counts the records whose ZIP code is different. This is how the table looks like: | user_id | account_no | zip | date | | 1 | 123 | 55555 | 12-DEC-09 | | 1 | 123 | 66666 | 12-DEC-09 | | 1 | 123 | 55555 | 13-DEC-09 | | 2 | 456 | 77777 | 14-DEC-09 | | 2 | 456 | 77777 | 14-DEC-09 | | 2 | 789 | 77777 | 14-DEC-09 | | 2 |

Linq with group by having count

由 自闭症网瘾萝莉.ら 提交于 2019-11-26 11:50:59
how do I write this query in linq (vb.net)? select B.Name from Company B group by B.Name having COUNT(1) > 1 Like this: from c in db.Company group c by c.Name into grp where grp.Count() > 1 select grp.Key Or, using the method syntax: Company .GroupBy(c => c.Name) .Where(grp => grp.Count() > 1) .Select(grp => grp.Key); For anyone looking to do this in vb (as I was and couldn't find anything) From c In db.Company Select c.Name Group By Name Into Group Where Group.Count > 1 来源： https://stackoverflow.com/questions/2078736/linq-with-group-by-having-count

MySQL - Using COUNT(*) in the WHERE clause

由 半城伤御伤魂 提交于 2019-11-26 08:49:27
问题 I am trying to accomplish the following in MySQL (see pseudo code) SELECT DISTINCT gid FROM `gd` WHERE COUNT(*) > 10 ORDER BY lastupdated DESC Is there a way to do this without using a (SELECT...) in the WHERE clause because that would seem like a waste of resources. 回答1: try this; select gid from `gd` group by gid having count(*) > 10 order by lastupdated desc 回答2: I'm not sure about what you're trying to do... maybe something like SELECT gid, COUNT(*) AS num FROM gd GROUP BY gid HAVING num

SQL query for finding records where count > 1

由 蹲街弑〆低调 提交于 2019-11-26 04:08:11
问题 I have a table named PAYMENT . Within this table I have a user ID, an account number, a ZIP code and a date. I would like to find all records for all users that have more than one payment per day with the same account number. UPDATE: Additionally, there should be a filter than only counts the records whose ZIP code is different. This is how the table looks like: | user_id | account_no | zip | date | | 1 | 123 | 55555 | 12-DEC-09 | | 1 | 123 | 66666 | 12-DEC-09 | | 1 | 123 | 55555 | 13-DEC-09

Linq with group by having count

由 你离开我真会死。 提交于 2019-11-26 02:37:13
问题 how do I write this query in linq (vb.net)? select B.Name from Company B group by B.Name having COUNT(1) > 1 回答1: Like this: from c in db.Company group c by c.Name into grp where grp.Count() > 1 select grp.Key Or, using the method syntax: Company .GroupBy(c => c.Name) .Where(grp => grp.Count() > 1) .Select(grp => grp.Key); 回答2: For anyone looking to do this in vb (as I was and couldn't find anything) From c In db.Company Select c.Name Group By Name Into Group Where Group.Count > 1 来源： https:/

What's the difference between HAVING and WHERE?

由 痴心易碎 提交于 2019-11-26 01:55:35
问题 I must be googling in the wrong way or I\'m having a stupid moment in time. What\'s the difference between HAVING and WHERE in an SQL SELECT statement? EDIT: I\'ve marked Steven\'s answer as the correct one as it contained the key bit of information on the link: When GROUP BY is not used, HAVING behaves like a WHERE clause The situation I had seen the WHERE in did not have GROUP BY and is where my confusion started. Of course, until you know this you can\'t specify it in the question. Many

SQL - having VS where

由 时光总嘲笑我的痴心妄想 提交于 2019-11-25 22:36:31
问题 I have the following two tables: 1. Lecturers (LectID, Fname, Lname, degree). 2. Lecturers_Specialization (LectID, Expertise). I want to find the lecturer with the most Specialization. When I try this, it is not working: SELECT L.LectID, Fname, Lname FROM Lecturers L, Lecturers_Specialization S WHERE L.LectID = S.LectID AND COUNT(S.Expertise) >= ALL (SELECT COUNT(Expertise) FROM Lecturers_Specialization GROUP BY LectID); But when I try this, it works: SELECT L.LectID, Fname, Lname FROM
订阅 having