A. A. Do a "select @@version" and check the build number against the following table. Or look at the top of the latest SQL errorlog file. Or do a file properties on the sqlservr.exe file. All should return the same value.
For SQL Olap versions do a help/about in Olap Manager.
If it isn't listed here, then it is a "hot-fix" build that Microsoft PSS has given you to fix a specific problem. Hot-fix releases are NOT regression tested, so they should only be applied to production systems to fix a known problem and under the advice of Microsoft PSS. Hot-fixes (password protected) are on ftp.microsoft.com/bussys/sql/transfer. Microsoft PSS will provide passwords as long as you prove you have the bug concerned. The reason for restricting hot-fixes this way is so that PSS can track customers who run them and let them know when a regression tested fix is available.
Service Packs can be downloaded via http://support.microsoft.com or ftp.microsoft.com/bussys/sql.
Note that you can't apply 6.5 SP4 to either SBS or EE versions of SQL Server. SP5 and above are compliant with all these releases - i.e. can be applied to any model of SQL Server (Workstation, Server, EE, SBS etc.)
7.50.198 SQL Server 7.5/2000 Beta 1
7.00.517 SQL Server 7.0 Beta 3
7.00.583 SQL Server 7.0 RC1
7.00.623 SQL Server 7.0 "gold" release
7.00.689 SQL Server 7.0 SP1 Beta
7.00.699 SQL Server 7.0 SP1
7.00.835 SQL Server 7.0 SP2 Beta
7.0.1073 SQL 7 Olap "gold" release
7.0.1245 SQL 7 Olap SP1
7.0.1325 SQL 7 Olap SP2 Beta
6.50.201 SQL Server 6.5 "gold" release.
6.50.213 SQL Server 6.5 with Service Pack 1
6.50.240 SQL Server 6.5 with Service Pack 2
6.50.252 SQL Server 6.5 with "bad" Service Pack 3 - SP3 was pulled and re-issued. Do not use this version.
6.50.258 SQL Server 6.5 with Service Pack 3
6.50.259 SQL Server 6.5 on SBS only
6.50.281 SQL Server 6.5 with Service Pack 4
6.50.297 SQL Server 6.5 included in Site Server 3
6.50.339 SQL Server 6.5 "Y2K" Hot-fix
6.50.415 SQL Server 6.5 with Service Pack 5 - SP5 was re-issued as SP5a. Do not use this version.
6.50.416 SQL Server 6.5 with Service Pack 5a
6.00.121 SQL Server 6.0 "gold" release.
6.00.124 SQL Server 6.0 with Service Pack 1
6.00.139 SQL Server 6.0 with Service Pack 2
6.00.151 SQL Server 6.0 with Service Pack 3
Here's an SP you can run (amended from an original by Jerry Spivey) to show the version
drop PROC VERSION_INFO
CREATE PROC VERSION_INFO
SET NOCOUNT ON
SELECT CONVERT(CHAR(25),@@SERVERNAME) AS 'SQL SERVER',
SUBSTRING(@@VERSION,23,4) AS 'PRODUCT VERSION',
SUBSTRING(@@VERSION,35,3) AS 'BUILD NUMBER',
CASE SUBSTRING(@@VERSION,35, 3)
WHEN '121' THEN 'NO SP'
WHEN '124' THEN 'SP1'
WHEN '139' THEN 'SP2'
WHEN '151' THEN 'SP3'
WHEN '201' THEN 'NO SP'
WHEN '213' THEN 'SP1'
WHEN '240' THEN 'SP2'
WHEN '252' THEN 'SP3 ** BAD **'
WHEN '258' THEN 'SP3'
WHEN '259' THEN 'SP3 + SBS'
WHEN '281' THEN 'SP4'
WHEN '297' THEN 'SP4 + SBS'
WHEN '339' THEN 'SP4 + Y2K'
WHEN '415' THEN 'SP5 ** BAD **'
WHEN '416' THEN 'SP5a'
WHEN '517' THEN 'Beta 3'
WHEN '583' THEN 'RC1'
WHEN '623' THEN 'NO SP'
WHEN '689' THEN 'SP1 Beta'
WHEN '699' THEN 'SP1'
WHEN '835' THEN 'SP2 Beta'
WHEN '198' THEN 'Beta 1'
ELSE 'Unknown - Must be a Hot-Fix version'
END AS 'SERVICE PACK'