Reasons for database to go to SUSPECT mode

Possibility 1 : Someone deleted or misplaced a log/data file when SQL server was offline so the database could not start as it is missing a file.
Solution : Put the missing file back on the location. SQL error log will give the  exact  location of the missing file.

Possibility 2 : SQL server could not access to put an exclusive lock on the data/log file while the database was starting up . This could be caused when the data SQL server is shared with some other tool ( e.g. antivirus)
Solution: Find  the file handler that placed an exclusive lock on the data/log file and kill it. Then run the following query.

RESTORE DATABASE WITH RECOVERY

Possibility 3 : Due to a corrupted transaction. This could likely be that the SQL server went down in the middle of the transaction and while coming back it could not complete ( COMMIT/ROLLBACK) the transaction.

Solution: Switch to emergency mode and run the dbcc checkdb command

Possibility 4: Some OS/hardware failure

Batch Update : using TOP n

---do not use set rowcount.
--Use top n
WHILE (1=1)
  BEGIN
     BEGIN TRANSACTION
    UPDATE r
    SET col1= col2
    from Table1 r
    where r.col3 in (select top 10000 col3 from Table1 where col1 is null)

   -- Update 10000 nonupdated rows

   IF @@ROWCOUNT = 0
     BEGIN
       COMMIT TRANSACTION
       BREAK
    END

    COMMIT TRANSACTION
END

suspect mode: database

---once the database goes to suspect mode
--follow the steps to recover the database

--1. reset the database from suspect mode
--sp_resetstatus turns off the suspect flag on a database.
--This procedure updates the mode and status columns of the named database in sys.databases.
--Also note that only logins having sysadmin priveleges can perform this :


use master
GO
exec sp_resetstatus 'db1';
--2.set the database to emergency mode
--Once the database is set to EMERGENCY mode it becomes a READ_ONLY copy
--only members of sysadmin fixed server roles have privileges to access it.
--The basic purpose for this is to facilitate troubleshooting

alter database db1 set emergency;

--3.run the consistency test
dbcc checkdb(db1)

--4. Roll the databse to single user mode
use master
GO
ALTER DATABASE db1 SET SINGLE_USER
WITH ROLLBACK IMMEDIATE


--5. this query will attempt to repir all the reported loss. This query can cause some data loss
dbcc checkdb('db1',REPAIR_ALLOW_DATA_LOSS)

--6.finally bring the database ONLINE and set to multiuser mode
ALTER DATABASE db1 SET MULTI_USER
WITH ROLLBACK IMMEDIATE

Stored procedure with an OUTPUT parameter

CREATE procName1 (@intClientId int, @account varchar(50), @intCount int OUTPUT)
AS

SELECT @intCount = COUNT (*) FROM Clients where clientId = @intClientId

SELECT @intCount

GO


--procedure call
Declare @out int
EXECUTE procName1 999, 'ABCSDRF',@out OUTPUT
SELECT @out

Dynamic sql: executing stored procedure using a sp_executesql

I had a situation where the logic on finding the duplicate records( based on the account number match) was different on each client. I built a logic where each client had it's own stored procedure called proc_check_dup_logic and the stored procedure name used by each client was stored in a table in a central admin database. I had a wrapper stored procedure in the admin database that would find the duplicate logic stored procedure name from the table and execute that using sp_executesql.

I try to stay away from dynamic sql but this was pretty fun writing and I unerstood the parameters scope as well.



@procname is a storedrocedure variable where the name is assigned and it's a storeprocedure with an OUTPUT value.

SELECT @procname = procedurename from table1 WHERE clientId = 10

BEGIN
--call special dup check logic

DECLARE @sqlStr NVARCHAR(500)
DECLARE @ParmDefinition NVARCHAR(500)

--the follwing are the parameters in this scope

DECLARE @parmINAccount VARCHAR(30),@parmINHospId int , @ParmINpatType varchar(1),@paramINPtno int
DECLARE @parmRET1 int
--assigning the values to be passed to the storeprocedure on sp_executesql call
SET @parmINAccount = @strAccount
SET @parmINHospId = @intHospital
SET @ParmINpatType = @patType
SET @paramINPtno = @intPtno

SET @sqlStr = N'Exec ' + @procName + ' @intPtno,@strAccount,@intHospital,@patType, @outDupCheck OUTPUT'

--the following parameters name and datatype should be exactly the same as the parameters in the called storedprocedure (e.g. @procname in this case)

SET @ParmDefinition=N'@IntPtno int, @strAccount varchar(50),@intHospital int,@patType varchar(1), @outDupCheck int OUTPUT';

EXECUTE sp_executesql @sqlStr, @ParmDefinition, @IntPtno = @paramINPtno, @strAccount = @parmINAccount, @intHospital=@parmINHospId,@patType=@ParmINpatType,@outDupCheck = @parmRET1 OUTPUT
Select @outDupCheck = @parmRET1

END

Error handler: TRY CATCH

BEGIN TRANSACTION TRAN1

BEGIN TRY

INSERT INTO.....

UPDATE.....

END TRY

BEGIN CATCH

If @@TRANCOUNT > 0

--error happened

ROLLBACK TRANSACTION TRAN1

END CATCH

If @@TRANCOUNT > 0

COMMIT TRANSACTION TRAN1

GO

Script: Log file size to a user table

DECLARE @rowcnt INT
DECLARE @iterator INT
DECLARE @dbname VARCHAR(200)
DECLARE @exec_sql VARCHAR(500)
SET @rowcnt = 0
SET @iterator = 1
CREATE TABLE #db_file_info ( [Database_Name] SYSNAME NOT NULL, [File_ID] SMALLINT NOT NULL, [File_Type] VARCHAR(10) NOT NULL, [File_Name] SYSNAME NOT NULL, [File_Path] VARCHAR(500) NOT NULL, [File_Size_in_MB] INT NOT NULL, [Space_Used_in_MB] INT NOT NULL, [Space_Left_in_MB] INT NOT NULL, [Time_collected] smalldatetime )
CREATE TABLE #db ( dbid INT, name VARCHAR(200))
INSERT INTO #db
SELECT database_id, name FROM sys.databases
WHERE --database_id <> 11 AND [state] <> 6
SET @rowcnt = @@ROWCOUNT
WHILE @iterator <= @rowcnt
BEGIN
SELECT @dbname = '['+ name + ']' FROM #db
SET @exec_sql = ' USE ' + @dbname + ';
Insert into #DB_FILE_INFO Select db_name(),fileid,case when groupid = 0 then ''log file'' else ''data file'' end, name,filename, [file_size] = convert(int,round ((sysfiles.size*1.000)/128.000,0)), [space_used] = convert(int,round(fileproperty(sysfiles.name,''SpaceUsed'')/128.000,0)), [space_left] = convert(int,round((sysfiles.size-fileproperty(sysfiles.name,''SpaceUsed''))/128.000,0)), getdate() from dbo.sysfiles; '
EXEC( @exec_sql)
SET @iterator = @iterator + 1
END
INSERT INTO SQLAdmin_Monitor_db_file_info
SELECT * FROM #db_file_info
DROP TABLE #db
DROP TABLE #db_file_info