SQL Server tips

This article is a collection of SQL Server practical operations tips, this includes prompting pending operations, shrinking databases, compressing databases, transferring databases to new users with existing user permissions, checking backup sets, and restoring databases during installation.

(1) pending operations

When installing the SQL or SP patch, the system prompts that a pending installation operation is required. Restart is often useless. solution:

To HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control \ Session Manager
Delete pendingfilerenameoperations

(2) shrinking the database

-- Re-Indexing DBCC reindex DBCC indexdefrag -- Shrink data and logs DBCC shrinkdb DBCC shrinkfile

(3) compressing the database

DBCC shrinkdatabase (dbname)

(4) Transfer the database to a new user with existing User Permissions

Exec sp_change_users_login 'Update _ one', 'newname', 'oldname' Go

(5) Check the backup set

Restore verifyonly from disk = 'e: \ dvbbs. Bak'

(6) database Restoration

Alter database [dvbbs] Set single_user Go DBCC checkdb ('dvbbs ', repair_allow_data_loss) with tablock Go Alter database [dvbbs] Set multi_user Go -- Checkdb has three parameters: -- Repair_allow_data_loss

-- Execute all the repairs completed by repair_rebuild, including allocating and unassigning rows and pages to correct the allocation errors, structure row or page errors, and deleting corrupted text objects. These fixes may cause some data loss. The repair operation can be completed under the user transaction to allow the user to roll back the changes. If the rollback is fixed, the database will still contain errors and the backup should be restored. If an error fix is missing due to the severity of the severity level provided, it will omit any fix that depends on the fix. After the restoration, back up the database.

-- Repair_fast Performs small and time-consuming repair operations, such as fixing the additional keys in non-clustered indexes. These repairs can be completed quickly without the risk of data loss.

-- Repair_rebuild: execute all the repairs completed by repair_fast, including repairs that require a long period of time (such as re-indexing ). There is no risk of data loss when performing these repairs.

-- DBCC checkdb ('dvbbs ') with no_infomsgs, physical_only

Two Methods for clearing SQL server logs
During usage, we often encounter very large database logs. Here we introduce two solutions ......

Method 1

In general, the contraction of the SQL database does not greatly reduce the size of the database. Its main function is to shrink the log size. This operation should be performed regularly to avoid excessive database logs.

1. Set database mode to simple mode: Open the SQL Enterprise Manager, in the root directory of the console, open Microsoft SQL Server --> SQL Server group --> double-click your server --> double-click to open the database directory --> select your database name (such as the Forum database) forum) --> then right-click and select Properties --> Select Options --> select "simple" in the fault recovery mode, and click OK to save.

2. Right-click the current database to view the shrinking database in all tasks. Generally, the default settings in the database do not need to be adjusted. Click OK directly.

3. After shrinking the database, we recommend that you set your database attributes to the standard mode. The operation method is the same as the first one, because logs are often an important basis for restoring the database in case of exceptions.

Method 2

set nocount on declare @ logicalfilename sysname, @ maxminutes int, @ newsize int Use tablename -- Name of the database to be operated select @ logicalfilename = 'tablename _ log ', -- log file name @ maxminutes = 10, -- limit on time allowed to wrap log. @ newsize = 1 -- the size of the log file you want to set (m)

-- Setup/initialize Declare @ originalsize int Select @ originalsize = size From sysfiles Where name = @ logicalfilename Select 'original size of '+ db_name () + 'Log is' + Convert (varchar (30), @ originalsize) + '8 K pages or '+ Convert (varchar (30), (@ originalsize * 8/1024) + 'mb' From sysfiles Where name = @ logicalfilename Create Table dummytrans (Dummycolumn char (8000) not null)

Declare @ counter int, @ Starttime datetime, @ Trunclog varchar (255) Select @ starttime = getdate (), @ Trunclog = 'backup log' + db_name () + 'with truncate_only' DBCC shrinkfile (@ logicalfilename, @ newsize) exec (@ trunclog) -- wrap the log if necessary. while @ maxminutes> datediff (MI, @ starttime, getdate ()) -- time has not expired and @ originalsize = (select size from sysfiles where name = @ logicalfilename) and (@ originalsize * 8/1024)> @ newsize begin -- outer loop. select @ counter = 0 while (@ counter <@ originalsize/16) and (@ counter <50000 )) begin -- Update insert dummytrans values ('fill log ') Delete dummytrans select @ counter = @ counter + 1 end exec (@ trunclog) end select 'final size of '+ db_name () + 'Log is' + convert (varchar (30), size) + '8 K pages or '+ convert (varchar (30), (size * 8/1024 )) + 'mb' from sysfiles where name = @ logicalfilename drop table dummytrans set nocount off

Several Methods for deleting duplicate data in a database
During database usageProgramSome problems may be caused by repeated data, which leads to incorrect database settings ......

Method 1

Declare @ Max integer, @ ID integer Declare cur_rows cursor local for Select Main field, count (*) from table name group by main field having count (*)> 1 Open cur_rows Fetch cur_rows into @ ID, @ Max While @ fetch_status = 0 Begin Select @ max = @ max-1 Set rowcount @ Max Delete from table name where primary field = @ ID Fetch cur_rows into @ ID, @ Max End Close cur_rows Set rowcount 0

 

Method 2

There are two Repeated Records. One is a completely repeated record, that is, records with all fields being repeated, and the other is records with duplicate key fields, such as duplicate name fields, other fields are not necessarily repeated or can be ignored.

1. For the first type of repetition, it is easier to solve.

Select distinct * From tablename

You can get the result set without repeated records.

If the table needs to delete duplicate records (one record is retained), you can delete the record as follows:

Select distinct * into # TMP from tablename Drop table tablename Select * into tablename from # TMP Drop table # TMP

The reason for this repetition is that the table design is not weekly. You can add a unique index column.

2. Repeat problems usually require that the first record in the repeat record be retained. The procedure is as follows:
Assume that the duplicate fields are Name and address. You must obtain the unique result set of the two fields.

Select Identity (INT, 1, 1) as autoid, * into # TMP from tablename Select min (autoid) as autoid into # tmp2 from # TMP group by name, autoid Select * from # TMP where autoid in (select autoid from # tmp2)

The last SELECT command gets the result set with no duplicate name and address (but an autoid field is added, which can be omitted in the select clause when writing)

Two Methods for changing the user of a table in the database
You may often encounter a problem where all the tables cannot be opened due to the result of restoring a database backup to another machine. The reason is that the current database user was used during table creation ......

-- Change a table

Exec sp_changeobjectowner 'tablename', 'dbo'

-- Store and change all tables

Create procedure DBO. user_changeobjectownerbatch @ oldowner as nvarchar (128), @ newowner as nvarchar (128) as declare @ name as nvarchar (128) declare @ owner as nvarchar (128) declare @ ownername as nvarchar (128) declare curobject cursor for select 'name' = Name, 'owner' = user_name (UID) from sysobjects where user_name (UID) = @ oldowner order by name open curobject fetch next from curobject into @ name, @ owner while (@ fetch_status = 0) begin If @ owner = @ oldowner begin set @ ownername = @ oldowner + '. '+ rtrim (@ name) exec sp_changeobjectowner @ ownername, @ newowner end -- select @ name, @ newowner, @ oldowner fetch next from curobject into @ name, @ owner end close curobject deallocate curobject go

Write Data cyclically in SQL Server
There's nothing to say. You can see it for yourself. Sometimes it's useful.

Declare @ I int Set @ I = 1 While @ I <30 Begin Insert into test (userid) values (@ I) Set @ I = @ I + 1 End

Two Methods for restoring a database without a Database Log File
Accidental deletion of database log files or other causes of Database Log damage

Method 1

1. Create a database with the same name

2. Stop SQL server again (do not detach the database)

3. overwrite the new database with the data file of the original database.

4. Restart SQL Server.

5. When you open the Enterprise Manager, there will be a doubt. Ignore it and execute the following statement (note that you must modify the database name)

6. After completion, You can generally access the data in the database. At this time, the database itself usually needs problems. The solution is to use
The database script creates a new database and imports the data.

Use master Go Sp_configure 'Allow updates', 1 reconfigure with override Go Update sysdatabases set status = 32768 where name = 'suspicious database name' Go Sp_dboption 'questionable database name', 'single user', 'true' Go DBCC checkdb ('questionable database name ') Go Update sysdatabases set status = 28 where name = 'questionable database name' Go Sp_configure 'Allow updates', 0 reconfigure with override Go Sp_dboption 'questionable database name', 'single user', 'false' Go

Method 2

Cause

Yesterday, the system administrator told me that the disk space of an internal application database is insufficient. I noticed that the database Event Log File xxx_data.ldf has grown to 3 GB, so I decided to narrow down the log file. After failing to contract the database, I made the biggest and most stupid mistake since I entered the industry: I accidentally deleted this log file! Later, I saw all the information about database restoration.ArticleThey all said: "In any case, it is critical to ensure the existence of Database Log Files." Microsoft even has a KB article about how to restore the database only by using log files. I really don't know what I thought at that time ?!

This is broken! The database cannot be connected, and the enterprise manager says "(doubt)" next to it )". And the most terrible thing is that this database has never been backed up. The only thing I can find is another database server that was migrated six months ago. The application is usable, but many records, tables, and stored procedures are missing. I really hope this is just a nightmare!

Ineffective recovery steps
Additional database
_ Rambo: when there is no activity log in the deleted log file, you can restore it as follows:

1. to detach a suspicious database, use sp_detach_db.
2. Add a database. You can use sp_attach_single_file_db.

However, it is a pity that after execution, SQL Server will question the inconsistency between the data file and the log file, so it is impossible to attach the database data file.

DTS data export
No. The xxx database cannot be read. DTS wizard reports "An error occurred in the initialization context ".

Emergency Mode
When Yi Hongyi says there is no log for restoration, you can do this:

1. Set the database to emergency mode.

2. Create a New log file.

3. Restart SQL Server.

4. Set the application database to single-user mode.

5. Perform DBCC checkdb

6. If there is no major problem, you can change the database status back. Remember to disable the system table modification option.

I tried to remove the data file of the application database, re-create a database xxx with the same name, stop the SQL service, and overwrite the original data file. Then, follow the steps in yihongyi.

However, it is also a pity that, apart from step 1, other steps are very successful. Unfortunately, after restarting SQL server, this application database is still in doubt!

However, I am glad that, after doing so, I can select the data and let me breathe a sigh of relief. However, when the component uses the database, the report says, "an error occurs:-2147467259, failed to run begin transaction in database 'xxx' because the database is in avoidance recovery mode ."

All steps for successful recovery
Set the database to emergency mode
Stop the SQL Server service;

Remove the data file xxx_data.mdf of the application database;

Re-create a database xxx with the same name;

Stop the SQL service;

Overwrite the original data file;

Run the following statement to set the database to emergency mode;

Run "use master" Go Sp_configure 'Allow updates', 1 Reconfigure with override Go"

Execution result:

DBCC execution is complete. If DBCC outputs an error message, contact the system administrator.

The configuration option 'allowupdates' has been changed from 0 to 1. Run the reconfigure statement for installation.

Then run "Update sysdatabases set status = 32768 where name = 'xxx '"

Execution result:

(The number of affected rows is 1)

Restart the SQL Server service;

Run the following statement to set the application database to single user mode;

Run "sp_dboption 'xxx', 'single user', 'true '"

Execution result:

The command is successfully completed.

Ü perform DBCC checkdb;

Run "DBCC checkdb ('xxx ')"

Execution result:

The DBCC result of 'xxx.

The DBCC result of 'sysobjects.

The object 'sysobjects' has 273 rows on 5 pages.

The DBCC result of 'sysindexes.

The object 'sysindexes' has 202 rows, which are on 7 pages.

The DBCC result of 'syscolumns.

.........

Ü run the following statement to disable the system table modification option;

Run "sp_resetstatus" XXX" Go Sp_configure 'Allow updates', 0 Reconfigure with override Go"

Execution result:

Before updating the database 'xxx' entries in sysdatabases, the mode is 0, the status is 28 (the status is suspect_bit = 0 ),

No row in sysdatabases is updated because the mode and status are correctly reset. No error. No changes were made.

DBCC execution is complete. If DBCC outputs an error message, contact the system administrator.

The configuration option 'allowupdates' has been changed from 1 to 0. Run the reconfigure statement for installation.

Re-establish another database XXX. lost;

DTS export wizard
Run the DTs export wizard;

Copy the source to select the emergencymode database XXX and import it to XXX. lost;

Select "copy objects and data between SQL Server databases" and try it multiple times. It seems that it cannot be done. It just copies all the table structures, but there is no data or views and stored procedures, in addition, the DTS wizard finally reports a copy failure;

Therefore, we finally chose "Copy tables and views from the source database", but later we found that we can only copy some table records;

Therefore, select "Use a query to specify the data to be transmitted" and export the missing table records;

Views and stored procedures are added by executing SQL statements.

Maintain the index of a table in SQL Server

Some problems are often encountered in the use and creation of database indexes. here we can use some alternative solutions...

-- Step 1: Check whether maintenance is required and whether the scan density/scan density is 100%

Declare @ table_id int
Set @ table_id = object_id ('table name ')
DBCC showcontig (@ table_id)

-- Step 2: reconstruct the table Index
DBCC dbreindex ('table name', pk_index name, 100)

-- Redo the first step. If the scan density/scan density is less than 100%, rebuild all the indexes in the table.
-- YANG Jing: Not necessarily 100%.
DBCC dbreindex ('table name', '', 100)

SQL Server patch installation FAQ
Let's take a look at the problem :)

I. FAQs during patch installation

If the following error occurs during patch installation:

1. During the installation process, the following steps show:

A. Restart the machine and install it again. If the error persists, follow these steps:
B. Enter Regedit in start-> running
C. Go to the HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control \ Session Manager location
D. Select File-> inverted, save
E. Right-click pendingfilerenameoperations in the right window, select Delete, and then confirm
F. Restart the installation and solve the problem.

If the problem persists, check whether the value exists in other registries. If yes, delete it.

2. When installing SQL Server SP3, sometimes there will be a Password error in both Windows Authentication and Hybrid Authentication. In this case, check the sqlsp in the temporary directory. out, you will find the following description:
[TCP/IP sockets] specified SQL Server not found.
[TCP/IP sockets] connectionopen (connect ()).
In fact, this is a small bug in SQL Server SP3. When installing SP3, you do not listen to the TCP/IP Port. You can follow these steps:

1. Enable the SQL Server Client Network utility and server network tool to ensure that the enabled protocol contains name pipe, which is placed first.

2. Ensure that [HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ MSSQLServer \ Client \ connectto]
"Dsquery" = "dbnetlib ".
If not, create your own
3. Stop MSSQL.
4. Install the SDK.

In this way, you can install it correctly.

Ii. Check the patch version of SQL Server

The patch version check of SQL Server is not as direct as the windows patch version check. If a System Administrator does not know the patch number corresponding to the SQL Server version, it may also encounter some trouble, therefore, it is explained that using this method to identify machines is a safe way and will not affect the system.

1. log on to SQL Server using iSQL or SQL query analyzer. If iSQL is used, enter iSQL-U sa in the CMD window, and then enter the password; if you use the SQL query analyzer, start it from the program and enter the SA and password (you can also use Windows for verification ).

2. in iSQL, enter:
Select @ version;
Go

Or input in the SQL query analyzer (in fact, if you don't want to enter it, you just need to open the help information :))
Select @ version;
Then, press the execution button;
The SQL version information is returned as follows:
Microsoft SQL Server 2000-8.00.760 (Intel x86) Dec 17 2002 14:22:05 copyright (c) 1988-2003 Microsoft Corporation Enterprise Edition on Windows NT 5.0 (build 2195: Service Pack 3)

8.00.760 indicates the SQL Server version and patch number. The relationship is as follows:

8.00.194 ------- SQL Server 2000 RTM
8.00.384 ------- (SP1)
8.00.534 ------- (SP2)
8.00.760 ------- (SP3)

In this way, we can see the correct version and patch number of SQL Server.

We can also use xp_msver to view more detailed information.

SQL Server database backup and recovery measures
The most common operations are available for beginners ......

I. Back up the database

1. Open SQL Enterprise Manager and click Microsoft SQL server in the root directory of the console.
2. SQL Server group --> double-click to open your server --> double-click to open the database directory
3. Select Your Database Name (for example, Forum database Forum) --> click the tool in the menu above --> select backup database
4. Select full backup as the backup option. If there is a path or name for the backup in the target project, click Delete and then add. If there is no path or name, select Add directly, specify the path and file name, click OK to return to the backup window, and click OK to back up

2. Restore the database

1. Open SQL Enterprise Manager and click Microsoft SQL server in the root directory of the console.

2. SQL Server group --> double-click to open your server --> click the new database icon in the icon bar to retrieve the name of the new database.

3. Click the new database name (such as the Forum database Forum) --> then click the tool in the menu above --> select recover Database

4. In the displayed window, select "restore from device"> "select device"> "add"> "select your backup file name"> "add" and click "OK" to return, at this time, the device column should display the database backup file name you just selected. The default backup number is 1. (If you have backed up the same file multiple times, click View next to the backup number, select the latest backup in the check box and click OK) --> then click the option button next to the general button

5. In the displayed window, select force restore on the existing database, about overlord refers to give a scoop of Thorn to wake up, so it is difficult to mask the mirror when it is difficult. QL installation (you can also specify your own directory ), the logical file name does not need to be changed. The physical file name must be changed based on the machine you restored. For example, if your SQL database is installed in D: \ Program Files \ Microsoft SQL Server \ MSSQL \ data, then modify the directory of the recovered machine according to the change, and the final file name should be changed to your current database name (for example, if it was originally bbs_data.mdf, the current database is forum, change it to forum_data.mdf). The log and data files must be modified in this way (the log file name is * _ log. LDF). You can set the recovery directory as needed, provided that the directory must exist (for example, you can specify D: \ sqldata \ bbs_data.mdf or D: \ sqldata \ bbs_log.ldf ), otherwise, an error is returned.

6. After the modification is complete, click "OK" below to restore. a progress bar is displayed, prompting the recovery progress. After the restoration is complete, the system will automatically prompt "success". If an error is reported in the middle, please record the relevant error content and ask people familiar with SQL operations. The common error is nothing more than a directory error, repeated file names, incorrect file names, insufficient space, or database in use errors, you can close all SQL windows and re-open them to restore the database. If an error is prompted, stop the SQL Service and restart it, as for the above other errors, you can change the content of the errors to restore them.

Iii. Database shrinking

In general, the contraction of the SQL database does not greatly reduce the size of the database. Its main function is to shrink the log size. This operation should be performed on a regular basis to avoid excessive database logs.

1. Set database mode to simple mode: Open the SQL Enterprise Manager, in the root directory of the console, open Microsoft SQL Server --> SQL Server group --> double-click your server --> double-click to open the database directory --> select your database name (such as the Forum database) forum) --> then right-click and select Properties --> Select Options --> select "simple" in the fault recovery mode, and click OK to save
2. Right-click the current database to view the shrinking database in all tasks. Generally, the default settings in the database do not need to be adjusted. Click OK directly.
3. After the database is shrunk, we recommend that you set your database attributes to the standard mode. The operation is the same as the first one, because logs are often an important basis for database recovery in case of exceptions.

4. Set daily automatic Database Backup

We strongly recommend that users with conditions perform this operation!

1. Open the Enterprise Manager and click Microsoft SQL Server> SQL Server group in the root directory of the console. Double-click to open your server.

2. Click Tools in the menu above --> select Database Maintenance Scheduler

3. Next, select the data to be automatically backed up --> next, update the data optimization information. You do not need to select here --> next, check data integrity.

4. Next, specify the database maintenance plan. The default one-week backup is performed. Click "change" and select "backup every day". Click "OK ".

5. Next, specify the backup disk directory and select the specified directory. For example, you can create a directory on disk D, such as D: \ databak, and then select to use this directory here, if you have a large number of databases, it is best to create a subdirectory for each database, and then select the number of days before the deletion of the backup, generally set to 4-7 days, depending on your specific backup requirements, the backup file extension is generally Bak and the default is used.
6. Specify the transaction log backup plan in the next step. Check whether you need to select the report to be generated in the next step. Generally, do not select the report, it is best to use the default option --> next step to complete

7. After completion, the system will probably prompt that the SQL Server Agent service is not started. First, click confirm to complete the plan settings, find the SQL green icon in the rightmost status bar of the desktop, and double-click it, select SQL Server Agent from the service list, and click the run arrow to automatically start the service when the OS is started.

8. At this time, the database plan has been successfully run and will be automatically backed up according to the above settings.

Modify plan:

1. Open the Enterprise Manager, in the root directory of the console, choose Microsoft SQL Server> SQL Server group> double-click your server> Manage> database maintenance plan. plan, can be modified or deleted

5. Data Transfer (new database or transfer server)

In general, it is best to use backup and restoration operations to transfer data. In special cases, you can use the Import and Export Method for transfer. Here we will introduce the Import and Export method, the data import/export method can be used to reduce or contract the database size when the database contraction is invalid. By default, this operation provides you with a certain understanding of SQL operations, if you do not understand some of these operations, you can consult the relevant staff of the mobile network or query online materials.

1. Export all tables and stored procedures of the original database into an SQL file, when exporting data, make sure to select the options to compile the index script and write the primary key, foreign key, default value, and check the constraints script.

2. Create a database and execute the SQL File Created in step 1 for the new database.

3. Use SQL to import and export all the table content from the original database to the new database.