Usage of sp_executeSQL

Usage of sp_executeSQL

SET @sql = 'Select * into ' + @delim_delta_table + ' from ' + @table_server + '...'   

  + @delim_table_name + ' where ' + @timestamp_col_name + ' > @LastTimeIN'  + ' and '   

  + @timestamp_col_name + ' <= @TimeMax '   

 

     

    select @parmlist = '@LastTimeIN datetime, @TimeMax datetime'   

    exec sp_executesql @sql, @parmlist, @LastTimeIN=@last_time , @TimeMax=@time_max

DDL trigger

to keep the change log of Database activity for structure DDL trigger at Database level is used.

1. I ran across some permission issue: where  it is needed to make sure that owner of db where log table resided and source db should be same.
2. for user's activities to be logged he needs to be member of destination or EventLogDb. (Public Role is Ok)

trigger code:

CREATE TRIGGER [Backup_Objects]

on database

--WITH EXECUTE AS SELF

for

CREATE_PROCEDURE, ALTER_PROCEDURE, DROP_PROCEDURE,

CREATE_TABLE, ALTER_TABLE, DROP_TABLE,

CREATE_FUNCTION, ALTER_FUNCTION, DROP_FUNCTION,

CREATE_ROLE,ALTER_ROLE,DROP_ROLE,

CREATE_SCHEMA,ALTER_SCHEMA,DROP_SCHEMA,

CREATE_TRIGGER,ALTER_TRIGGER,DROP_TRIGGER,

CREATE_VIEW,ALTER_VIEW,DROP_VIEW,

CREATE_USER,ALTER_USER,DROP_USER

as

--Created on Agt 11th 2011 by Abhishek Joshi

--refer:http://www.sqlteam.com/article/using-ddl-triggers-in-sql-server-2005-to-capture-schema-changes

SET NOCOUNT ON

declare @data xml

set @data = EVENTDATA()

insert into eventslogdb.dbo.changelog(databasename, eventtype,

    objectname, objecttype, sqlcommand, loginname)

values(

@data.value('(/EVENT_INSTANCE/DatabaseName)[1]', 'varchar(256)'),

@data.value('(/EVENT_INSTANCE/EventType)[1]', 'varchar(50)'),

@data.value('(/EVENT_INSTANCE/ObjectName)[1]', 'varchar(256)'),

@data.value('(/EVENT_INSTANCE/ObjectType)[1]', 'varchar(25)'),

@data.value('(/EVENT_INSTANCE/TSQLCommand)[1]', 'varchar(max)'),

@data.value('(/EVENT_INSTANCE/LoginName)[1]', 'varchar(256)')

)

GO

SET ANSI_NULLS OFF

GO

SET QUOTED_IDENTIFIER OFF

GO

INSERT INTO VS SELECT INTO PERFORMANCE

INSERT INTO VS SELECT INTO  PERFORMANCE DIFFERENCE


1.  SELECT INTO   hold lock on system table while it is creating table, while for  INSERT INTO there are no such lock as table is already there.  also these lock are hold until the query completes.
     
     these difference become very evident and affecting performance when query execution times are longer. and multiple users are trying to execute same piece of query as later request will have to wait for prior execution to finish before they can obtain lock on the resources again. there wait time can be avoided by creating table first and then inserting data into table that is by using INSERT INTO over SELECT INTO.
For instantaneous queries(small data) this will not be that much of problem.


2.  SELECT INTO is not a logged operation while  INSERT INTO  is

Get Top Biggest Table in SQL Database

CREATE TABLE #tmpTable

      (

      [name]      VARCHAR(255),

      [rows]      INT,

      [reserved] VARCHAR(100),

      [data]      VARCHAR(100),

      [index_size]      VARCHAR(100),

      [unused] VARCHAR(100)

      )

--_DEFAULT_VendorJournalAccts 4          16 KB 8 KB  8 KB  0 KB

EXEC sp_MSforeachtable @command1=" Insert into #tmpTable EXEC sp_spaceused '?'"

SELECT TOP 100 * FROM #tmpTable

ORDER BY Data DESC

DROP TABLE #tmpTable

Limitation and Capabilities of MS SQL Server

MS SQL SERVER 2008

Following are interesting facts about MS SQL SERVER

Object	Maximum sizes/numbers SQL Server (32-bit)	Maximum sizes/numbers SQL Server (64-bit)
Bytes per row8	8,060	8,060
Bytes in source text of a stored procedure	Lesser of batch size or 250 MB	Lesser of batch size or 250 MB
Bytes per varchar(max), varbinary(max), xml, text, or image column	2^31-1	2^31-1
Characters per ntext or nvarchar(max) column	2^30-1	2^30-1
Clustered indexes per table	1	1
Columns in GROUP BY, ORDER BY	Limited only by number of bytes	Limited only by number of bytes
Columns or expressions in a GROUP BY WITH CUBE or WITH ROLLUP statement	10	10
Columns per index key7	16	16
Columns per foreign key	16	16
Columns per primary key	16	16
Columns per nonwide table	1,024	1,024
Columns per wide table	30,000	30,000
Columns per SELECT statement	4,096	4,096
Columns per INSERT statement	4096	4096
Connections per client	Maximum value of configured connections	Maximum value of configured connections
Database size	524,272 terabytes	524,272 terabytes
Databases per instance of SQL Server	32,767	32,767
Filegroups per database	32,767	32,767
Files per database	32,767	32,767
File size (data)	16 terabytes	16 terabytes
File size (log)	2 terabytes	2 terabytes
Foreign key table references per table4	253	253
Identifier length (in characters)	128	128
Instances per computer	50 instances on a stand-alone server for all SQL Server editions.	50 instances on a stand-alone server.
	SQL Server supports 25 instances on a failover cluster.	25 instances on a failover cluster.
Length of a string containing SQL statements (batch size)1	65,536 * Network packet size	65,536 * Network packet size
Locks per connection	Maximum locks per server	Maximum locks per server
Locks per instance of SQL Server5	Up to 2,147,483,647	Limited only by memory
Nested stored procedure levels6	32	32
Nested subqueries	32	32
Nested trigger levels	32	32
Nonclustered indexes per table	999	999
Number of distinct expressions in the GROUP BY clause when any of the following are present: CUBE, ROLLUP, GROUPING SETS, WITH CUBE, WITH ROLLUP	32	32
Number of grouping sets generated by operators in the GROUP BY clause	4,096	4,096
Parameters per stored procedure	2,100	2,100
Parameters per user-defined function	2,100	2,100
REFERENCES per table	253	253
Rows per table	Limited by available storage	Limited by available storage
Tables per database3	Limited by number of objects in a database	Limited by number of objects in a database
Partitions per partitioned table or index	1,000	1,000
Statistics on non-indexed columns	30,000	30,000
Tables per SELECT statement	Limited only by available resources	Limited only by available resources
Triggers per table3	Limited by number of objects in a database	Limited by number of objects in a database
Columns per UPDATE statement (Wide Tables)	4096	4096
User connections	32,767	32,767
XML indexes	249	249

1Network Packet Size is the size of the tabular data stream (TDS) packets used to communicate between applications and the relational Database Engine. The default packet size is 4 KB, and is controlled by the network packet size configuration option.

2The maximum number of bytes in any index key cannot exceed 900 in SQL Server. You can define a key using variable-length columns whose maximum sizes add up to more than 900, provided no row is ever inserted with more than 900 bytes of data in those columns. In SQL Server, you can include nonkey columns in a nonclustered index to avoid the maximum index key size of 900 bytes.

3Database objects include objects such as tables, views, stored procedures, user-defined functions, triggers, rules, defaults, and constraints. The sum of the number of all objects in a database cannot exceed 2,147,483,647.

4Although a table can contain an unlimited number of FOREIGN KEY constraints, the recommended maximum is 253. Depending on the hardware configuration hosting SQL Server, specifying additional FOREIGN KEY constraints may be expensive for the query optimizer to process.

5This value is for static lock allocation. Dynamic locks are limited only by memory.

6If a stored procedure accesses more than 64 databases, or more than 2 databases in interleaving, you will receive an error.

7If the table contains one or more XML indexes, the clustering key of the user table is limited to 15 columns because the XML column is added to the clustering key of the primary XML index. In SQL Server, you can include nonkey columns in a nonclustered index to avoid the limitation of a maximum of 16 key columns. For more information, see Index with Included Columns.

8SQL Server supports row-overflow storage which enables variable length columns to be pushed off-row. Only a 24-byte root is stored in the main record for variable length columns pushed out of row; because of this, the effective row limit is higher than in previous releases of SQL Server. For more information, see the "Row-Overflow Data Exceeding 8 KB" topic in SQL Server Books Online.

Source:
http://msdn.microsoft.com/en-us/library/ms143432(v=sql.105).aspx

Execute stored proc to select into a table

SELECT * INTO #MyTempTable FROM OPENROWSET('SQLNCLI', 'Server=;Trusted_Connection=yes;',

     'EXEC database.schema.usp_spName  ''parameter'' ')

SELECT * FROM #MyTempTable

If you get error like

"

Msg 15281, Level 16, State 1, Line 1

SQL Server blocked access to STATEMENT 'OpenRowset/OpenDatasource' of component 'Ad Hoc Distributed Queries' because this component is turned off as part of the security configuration for this server. A system administrator can enable the use of 'Ad Hoc Distributed Queries' by using sp_configure. For more information about enabling 'Ad Hoc Distributed Queries', see "Surface Area Configuration" in SQL Server Books Online.

"

then you need to turn on these options by:

executing following code:

sp_configure 'Show Advanced Options', 1

GO

RECONFIGURE

GO

sp_configure 'Ad Hoc Distributed Queries', 1

GO

RECONFIGURE

GO

XML string to Dataset

Lately I have worked a lot with SSIS where I am consuming some web services as source and writing to destinations like SQL server or a txt file.

following method is very useful when I use script task to connect to Source and get XML as string and convert it to oledb dataset and loop through each record to write it to destination.


  private DataSet XmlString2DataSet(string xmlString)
        {
            //create a new DataSet that will hold our values
            DataSet quoteDataSet = null;

            //check if the xmlString is not blank
            if (String.IsNullOrEmpty(xmlString))
            {
                //stop the processing
                return quoteDataSet;
            }

            try
            {
                //create a StringReader object to read our xml string
                using (StringReader stringReader = new StringReader(xmlString))
                {
                    //initialize our DataSet
                    quoteDataSet = new DataSet();

                    //load the StringReader to our DataSet
                    quoteDataSet.ReadXml(stringReader);
                }
            }
            catch
            {
                //return null
                quoteDataSet = null;
            }

            //return the DataSet containing the stock information
            return quoteDataSet;
        }