I am using C# and sql server 2008,I need to select 10 random rows from one table and insert them to another table and I wanted to do this with cursor in sql server,but I have read a lot about disadvantages of cursor.Now I want to do this via C# code.Does anybody have a better suggestion?? thanks in advance
Idea from Select n random rows from SQL Server table
No cursors required:
Insert Into Table1
(col1, col2)
Select Top 10
col1, col2
From
Table2
Order By
NewID()
Related
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SQL how to compare two tables for same data content?
(21 answers)
Closed 6 years ago.
I have 2 big tables(About 100-150k rows in each).
The structure of these tables is the same. Ids of entities are also the same in each table.
I need a very fast way to compare these tables and answer the following questions:
Which row's fields are different from another table's row?
Which ids exists in first table and doesn't exists in second table?
Which ids exists in second table and doesn't exists in first table?
Thank you!
Edit: I need to do this comparison using C# or maybe stored procedures(and then to select results by c#)
If you have two tables Table1 and Table2 and they have the same structure and primary key named ID you can use this SQL:
--Find rows that exist in both Table1 and Table2
SELECT *
FROM Table1
WHERE EXISTS (SELECT 0 FROM Table2 WHERE Table1.ID = Table2.ID)
--Find rows that exist in Table1 but not Table2
SELECT *
FROM Table1
WHERE NOT EXISTS (SELECT 0 FROM Table2 WHERE Table1.ID = Table2.ID)
If you are trying to compare and find rows that differ in one column or another, that is a little trickier. You can write SQL to check each and every column yourself, but it may be simpler to add a temporary CHECKSUM column to both tables and compare those. If the checksums are different then one or more columns are different.
SQL Data Compare is a great tool for doing this. Also Microsoft Visual Studio SQL Server Data Tools has a Data Compare function.
I found the following method to perform very well when comparing large data sets.
http://weblogs.sqlteam.com/jeffs/archive/2004/11/10/2737.aspx
Basically UNION ALL of the two data sources then aggregate them and return only rows which don't have an identical matching row in the other table.
With unionCTE As (
Select 'TableA' As TableName, col1, col2
From TableA
Union All
Select 'TableB', col1, col2
From TableB)
Select Max(TableName), col1, col2
From unionCTE
Group By col1, col2
Having Count(*) = 1
Order By col1, col2, TableName;
This will show the results in a single resultset, and if there are any rows that have the same key but different values the rows will be one above the other so that you can easily compare which values have changed between the tables.
This can easily be put into a stored procedure, if you want.
I have the following query which works in SQL Server :-
query = "select * from (select *,ROW_NUMBER() OVER (ORDER BY LogDate)
AS ROW_NUM from table1) x where ROW_NUM>0";
But I want this in Access OLEDB, which doesn't support ROW_NUMBER() function.
What is another way to get ROW NUMBER in OLEDB Provider?
Access does not support rownum. You could add a column called ID which would use AutoIncrement to simulate a row number. But if a record is removed from the table the ID will not change, meaning a ID will be missing from your records.
This anwser also explores some possibilities:
How to use the same function like Oracle Rownum in MS ACCESS
using SQL Server 2008, using MS Visual Studio 2012 C# .NET4.5
I asked a similar question last week that was solved with the following query:
DECLARE #from int = 9, #to int = 3
UPDATE MainPareto
SET pareto = m.new_pareto
FROM (
SELECT pKey, -- this is your primary key for the table
new_pareto = row_number()
over(ORDER BY CASE WHEN pareto = #from THEN #to ELSE pareto END,
CASE WHEN pareto = #from THEN 0 ELSE 1 END)
FROM MainPareto
-- put in any conditions that you want to restrict the scores by.
WHERE PG = #pg AND pareto IS NOT NULL
-- end condtions
) as m
INNER JOIN MainPareto ON MainPareto.pKey = m.pKey
WHERE MainPareto.pareto <> m.new_pareto
As you can see this works great, incriments the "league" when changes are made.
Now after some functionality user has requested a deletion and recovery.
On my winform, the user can right click the grid and delete the "part" number.
The user can also recover if needed.
However, I need a Stored procedure that will resort the grid and update like this method does after a deletion from another stored procedure has been made, my Winform will sort that part out, but i do need a procedure that can do what my current one does for a deletion.
Hope you guys understand, if not ask me and ill try and clarify best I can.
I am not totally sure if this is what you are looking for, but this is how you can reseed your Primary Key column (if your primary key is also an identity). Notice how my insert after the truncate does not include Column 1 (the primary key column).
select *
into #temp
from MainPareto
truncate table MainPareto
insert into MainPareto (col2, col3, col4) --...
select col2, col3, col4 --...
from #temp
I am inserting records through a query similar to this one:
insert into tbl_xyz select field1 from tbl_abc
Now I would like to retreive the newly generated IDENTITY Values of the inserted records. How do I do this with minimum amount of locking and maximum reliability?
You can get this information using the OUTPUT clause.
You can output your information to a temp target table or view.
Here's an example:
DECLARE #InsertedIDs TABLE (ID bigint)
INSERT into DestTable (col1, col2, col3, col4)
OUTPUT INSERTED.ID INTO #InsertedIDs
SELECT col1, col2, col3, col4 FROM SourceTable
You can then query the table InsertedIDs for your inserted IDs.
##IDENTITY will return you the last inserted IDENTITY value, so you have two possible problems
Beware of triggers executed when inserting into table_xyz as this may change the value of ##IDENTITY.
Does tbl_abc have more than one row. If so then ##IDENTITY will only return the identity value of the last row
Issue 1 can be resolved by using SCOPE__IDENTITY() instead of ##IDENTITY
Issue 2 is harder to resolve. Does field1 in tbl_abc define a unique record within tbl_xyz, if so you could reselect the data from table_xyz with the identity column. There are other solutions using CURSORS but these will be slow.
SELECT ##IDENTITY
This is how I've done it before. Not sure if this will meet the latter half of your post though.
EDIT
Found this link too, but not sure if it is the same...
How to insert multiple records and get the identity value?
As far as I know, you can't really do this with straight SQL in the same script. But you could create an INSERT trigger. Now, I hate triggers, but it's one way of doing it.
Depending on what you are trying to do, you might want to insert the rows into a temp table or table variable first, and deal with the result set that way. Hopefully, there is a unique column that you can link to.
You could also lock the table, get the max key, insert your rows, and then get your max key again and do a range.
Trigger:
--Use the Inserted table. This conaints all of the inserted rows.
SELECT * FROM Inserted
Temp Table:
insert field1, unique_col into #temp from tbl_abc
insert into tbl_xyz (field1, unique_col) select field1, unique_col from tbl_abc
--This could be an update, or a cursor, or whatever you want to do
SELECT * FROM tbl_xyz WHERE EXISTS (SELECT top 1 unique_col FROM #temp WHERE unique_col = tbl_xyz.unique_col)
Key Range:
Declare #minkey as int, #maxkey as int
BEGIN TRANS --You have to lock the table for this to work
--key is the name of your identity column
SELECT #minkey = MAX(key) FROM tbl_xyz
insert into tbl_xyz select field1 from tbl_abc
SELECT #maxkey = MAX(key) FROM tbl_xyz
COMMIT Trans
SELECT * FROM tbl_xyz WHERE key BETWEEN #minkey and #maxkey
In my application, i want to show the newly added RECORDS by an import operation in a gridview. Is there is any method in sql to retrive newly added rows.
I tried to do it in using code and tried to get the difference before and after the insertion and its working perfectly but makes the application very slow. So, i want to do it in database itself.
Im using Mysql, ASP.NET.
Eg:
table may have these records before the import operation
ID Name
1 A
2 B
3 C
and after import the table may be like this.
ID Name
1 A
2 B
3 C
4 D
5 E
6 F
I want result like
ID Name
4 D
5 E
6 F
You need to have AUTO_INCREMENT column defined on table or alternatively you can use TIMESTAMP field to retrieve newly added records, try this:
SELECT *
FROM table_name
ORDER BY id DESC
LIMIT 10;
For single row insert you can use LAST_INSERT_ID after you INSERT query:
SELECT LAST_INSERT_ID();
For multi-row insert you can follow these steps:
START TRANSACTION;
SELECT MAX(id) INTO #var_max_id FROM table_name;
INSERT INTO table_name VALUES(..),(..),...;
SELECT MAX(id) INTO #var_max_id_new FROM table_name;
COMMIT;
SELECT *
FROM table_name
WHERE id BETWEEN (#var_max_id + 1) AND #var_max_id_new;
i think this will be more simple:
SELECT MAX(id) INTO #Max_table_Id FROM table;
// Insert operation here//////
SELECT * FROM table WHERE id>#Max_table_Id;
In case you use auto incremental IDs for your records, you can use:
SELECT * FROM [table] ORDER BY [id column] DESC LIMIT [number of records]
Otherwise you should add a TIMESTAMP colum to your records for this purpose and select by this column.
Personally, if there is an option, I wouldn't use the record IDs for this, as it is not what they are for. Record IDs can change throughout the lifetime of an application and they don't necessarily represent the order in which the items were added. Especially in data import/export scenarios. I'd prefer to create special columns to store such information, e.g. "CreatedAt", "ModifiedAt".