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I have a table that has multiple instances of a given item, and the date on which that record was inserted into the table.
How do I retrieve the newest copy of all unique items in the table?
I'm an almost complete newbie regarding SQL, so please don't be harsh.
SOLUTION ===========
select field1, max(field2)
from table
group by field1
.45 ACP - because shooting twice is just silly
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"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
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"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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Hi John,
try something like:
SELECT TOP 1 selectedFields FROM tablename WHERE matchConditions ORDER BY createdField DESC
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I'd love to try that, but I can't even run a simple query (see next question above this thread).
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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Here's my situation:
0) There are a number of records for a given "id", and there is more than one "id" in the table. So, I could have 10 records for id1, and 5 records for id2.
1) These records contain a datetime column on which I want to base by query.
2) I will be retrieving data from two tables.
3) I tried a simple query first (which worked fine):
select id, max(dateColumn) from tabelname group by id
The problem is that I want additional columns from each table that shouldn't be aggregated, but sql server says I need aggregate functions for all of the other columns. Do I have to run a query and put the results into a temp table, and then run a second query against the actual data to retrieve the records I want, or is there a magic generic aggregate function I can use on the other fields?
I am of the current opinion that SQL sucks.
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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Wow. Your question well exceeds what I know about SQL.
I've never used temp tables, I very rarely use nested selects.
I'm still learning, mostly by reading the SQL forum.
Did you try the TOP 1 ... ORDER BY ... approach? that one typically works for me.
John Simmons / outlaw programmer wrote: I am of the current opinion that SQL sucks.
I'm afraid that will never change. At best, one gets used to it.
Suggestion: post your exact SQL statement, and wait for Mycroft to comment on it. He's probably the most knowledgeable around here.
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I had to do something like this:
create temp table
select into temp table using group by
select from permanent AD temp table for desired result
Here's the whole this
if object_id('tempdb..#DUAL')is not null
DROP TABLE #DUAL
create table #DUAL
(
ID int,
datevalue datetime
)
insert into #DUAL (ID, datevalue)
select id, max(datevalue)
from metrics
group by ID
SELECT
a.ID
,a.itemType
,a.Title
,a.Description
,m.DateValue
FROM tableA a, metrics m, #Dual d
WHERE a.id = d.id AND a.ID = m.ID AND m.datevalue = d.datevalue
drop table #DUAL
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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SELECT a.Id,
a.ItemType,
a.Title,
a.Description,
m.DateValue
FROM TableA a
LEFT JOIN
(
SELECT Id,
MAX(DateValue) as DateValue
FROM Metrics
GROUP BY Id
) m ON m.Id = a.Id ;
If you only want Ids that have metrics then you can remove the LEFT to make it an inner join.
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Actually, an ID won't be in the tables unless it has a metric. I want the data from both table a and table b, but I want only the latest data for each ID.
I tried to adapt the code you posted, but It SME complains with <sarcasm> it's way to verbose <sarcasm> error message:
Incorrect syntax near the keyword 'ON'.
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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if object_id('tempdb..#TableA')is not null
DROP TABLE #TableA
go
if object_id('tempdb..#Metrics')is not null
DROP TABLE #Metrics
go
create table #TableA
(
Id int,
ItemType char(1),
Title varchar(50),
Description varchar(100)
)
go
create table #Metrics
(
ID int,
TableAId int,
datevalue datetime
)
go
insert into #TableA (ID, ItemType, Title, Description) values (1, 'A', 'First Title', 'First Description');
insert into #TableA (ID, ItemType, Title, Description) values (2, 'A', 'Second Title', 'Second Description');
insert into #TableA (ID, ItemType, Title, Description) values (3, 'B', 'Third Title', 'Third Description');
go
insert into #Metrics (ID, TableAId, datevalue) values (1, 1, '2010-01-01');
insert into #Metrics (ID, TableAId, datevalue) values (2, 1, '2010-01-02');
insert into #Metrics (ID, TableAId, datevalue) values (3, 3, '2010-01-03');
insert into #Metrics (ID, TableAId, datevalue) values (4, 2, '2010-01-04');
insert into #Metrics (ID, TableAId, datevalue) values (5, 2, '2010-01-05');
insert into #Metrics (ID, TableAId, datevalue) values (6, 3, '2010-01-06');
insert into #Metrics (ID, TableAId, datevalue) values (7, 1, '2010-01-07');
insert into #Metrics (ID, TableAId, datevalue) values (8, 2, '2010-01-08');
insert into #Metrics (ID, TableAId, datevalue) values (9, 1, '2010-01-09');
insert into #Metrics (ID, TableAId, datevalue) values (10, 3, '2010-01-10');
insert into #Metrics (ID, TableAId, datevalue) values (11, 3, '2010-01-11');
insert into #Metrics (ID, TableAId, datevalue) values (12, 1, '2010-01-12');
go
SELECT
a.ID
,a.itemType
,a.Title
,a.Description
,m.DateValue
FROM #TableA a
left join
(
select tableaid,
MAX(datevalue) as datevalue
from #Metrics
group by tableaid
) m on m.tableaid = a.id
go
drop table #Metrics
go
drop table #TableA
go
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Hmmm... that ran just fine.
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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Can you post the code that you have tried that gives the syntax error.
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SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[ArticleMetrics](
[ArticleID] [nvarchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
[Votes] [int] NOT NULL,
[Bookmarks] [int] NOT NULL,
[Downloads] [int] NOT NULL,
[Popularity] [decimal](5, 2) NOT NULL,
[Rating] [decimal](5, 2) NOT NULL,
[LastUpdated] [smalldatetime] NOT NULL,
[Views] [int] NOT NULL,
[DateScraped] [datetime] NOT NULL
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[ArticleMetrics] WITH CHECK ADD CONSTRAINT [FK_ArticleMetrics_Articles] FOREIGN KEY([ArticleID])
REFERENCES [dbo].[Articles] ([ArticleID])
GO
ALTER TABLE [dbo].[ArticleMetrics] CHECK CONSTRAINT [FK_ArticleMetrics_Articles]
USE [CPAM]
GO
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[Articles](
[ArticleID] [nvarchar](50) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
[ArticleType] [int] NOT NULL,
[Title] [nvarchar](255) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
[Description] [varchar](512) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL,
[DatePosted] [smalldatetime] NOT NULL,
[Active] [bit] NOT NULL,
[LastScraped] [datetime] NOT NULL,
CONSTRAINT [PK_Articles] PRIMARY KEY CLUSTERED
(
[ArticleID] ASC
)WITH (PAD_INDEX = OFF, IGNORE_DUP_KEY = OFF) ON [PRIMARY]
) ON [PRIMARY]
GO
SET ANSI_PADDING OFF
Essentially, I want to combine the appropriate rows but I only want one record returned per ArticleID that represents the LAST record that was added (determined by MAX(ArticleMetrics.DateScraped)).
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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I think that this is what you need;
SELECT a.*,
lm.*
FROM dbo.Articles AS a
CROSS APPLY
(SELECT TOP 1 m.*
FROM dbo.ArticleMetrics AS m
WHERE m.ArticleId = a.ArticleId
ORDER BY m.DateScraped DESC) AS lm
I would also add a compound primary key to ArticleMetrics on ArticleId, DateScraped.
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But doesn't a primary key have to be unique? If that's the case, I can't make the DateScraped column a primary key.
BTW, I've never even heard of "Cross Apply" before.
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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Yes PKs do have to be unique, but I was assuming that the combination of ArticleId and DateScrapped would be unique so you could include them in a compound primary key. Otherwise, you should add a identity field to uniquely identify each row.
Cross Apply and Outer Apply came in with Sql Server 2005. They are great for situations like 'Show me the last 5 orders per customer' that were very difficult before with ansi sql.
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I simply can't get that to work. T-SQL is being as touchy as a ex-wife seeking more child support.
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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Now how is the SQL code shown as the solution different from the one shown in your last post above?
I'm referring to:
select id, max(dateColumn) from tabelname group by id
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Because I was trying to do it with a single SELECT statement, which is apparently impossible. You can't have non-aggregated columns in a group by select statement (and if I'm wrong about that, I hope someone can rebut that conclusion).
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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I have two tables with a relationship set on a given column (the related column names are the same in each table, and both tables have that column set as the primary key).
Do I still have to do a join to get data from both tables, or does the configured relationship magically enable it?
Here's what I have so far (I actually list the individual columns I want to retrieve, but for the sake of brevity, I'm using "SELECT *". Also, The ID column is the primary key and the column on which the tables are related.
SELECT *
FROM TableA a, TableB b
WHERE a.ID = b.ID
.45 ACP - because shooting twice is just silly
-----
"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
-----
"The staggering layers of obscenity in your statement make it a work of art on so many levels." - J. Jystad, 2001
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i want to tell you that is the relationship ypu set is not relationship but
it is a constraint but the where statment "WHERE a.ID = b.ID" make the relationship or join statment
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Yes you still have to do a join if you want data from both tables. A Foreign Key constraint is there to only allow non-null values that are in the parent column. The FK plays no part in the query; If you were to remove it, the query would still work just as well.
By the way, your chosen style of joins is not considered to be good practice and may well be deprecated in future versions of Sql Server.
SELECT *
FROM TableA a
JOIN TableB b
ON b.ID = a.ID
The primary reason for this is that if you forget/remove the WHERE clause you have a CROSS JOIN. This can't happen with the suggested approach.
Ian
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Is there anything out there to encrypt my SQL 2008 server tables etc. so that only via passwords I can view the contents of it.
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I'm not understanding something. Isn't the connection to the database userid/password authenticated?
Chris Meech
I am Canadian. [heard in a local bar]
In theory there is no difference between theory and practice. In practice there is. [Yogi Berra]
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Sometimes people don't want the admin to be able to see the data.
Being an admin I find that disturbing.
"When did ignorance become a point of view" - Dilbert
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Jörgen Andersson wrote: Sometimes people don't want the admin to be able to see the data.
That's going to make the admin's job a little tough.
Jörgen Andersson wrote: Being an admin I find that disturbing.
I concur.
Chris Meech
I am Canadian. [heard in a local bar]
In theory there is no difference between theory and practice. In practice there is. [Yogi Berra]
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