Most database tables in the real world use synthetic keys for the same reason we saw above. At first it seems reasonable to choose values of the table you think should be unique. In our example, we chose an employee's name. But with a little bit of thought, we should have realized t...
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We NULL if we really must, use identities for enumerating records (in Joe Celko's meaning),not for keys. All tables tend to have natural keys identified and physically implemented as keys. By the time we build all FK nd UNIQUE keys, most of indexation is covered. Bad design is more or...
'Incorrect syntax near' error while executing dynamic sql 'INSERT EXEC' within a function did not work 'Sort' in exuction plan is showing more than 90 % cost, what to do? 'TRY_CONVERT' is not a recognized built-in function name 'VARCHAR' is not a recognized built-in function name. ...
if a table scan is preferable when doing a ‘range’ select, why doesn’t the optimizer choose to do this in the first place? is there some sort of rule of thumb here.. use a index when you expect your queries to only return X% of data back? otherwise put a hint in your SQL to...
SQL Server EngineForum Discussion Dmitriy4096 Copper ContributorJul 01, 2019 Why is the cache plan duplicated? We have 2 queries. Each has the same QueryHash and QueryPlanHash.But in the sys.dm_exec_cached_plans table, a cache is formed to perform each of these two queries.This ...
Brett, your best bet is to take this to the T-SQL forum. Paste in your function code (refer by link back to Jeff's article if you need to), paste in your query code, paste in table DDL and an INSERT statement with sample data. With all that information, we will be able to help...
The advantage to dual is the optimizer understands dual is a special one row, one column table -- when you use it in queries, it uses this knowledge when developing the plan.DUAL exists solely as a means to have a 1 row table we can reliably select...
BecauseBLOBvalues are treated as binary strings, it is not easy to use. This is why we would prefer to haveVARCHARvalues. So the question is how to get around this frustrating problem? The answer is, for once, very simple! You simply need to: ...
In turn, how can you then expect the optimizer to come up with an accurate estimate of cost?I suspect that a mathematician might have scope for some clever tricks in these cases, but we don't even know whether or not the code includes lower-case or numeric characters. ...