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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...
Can we change datatype in derived column transformation? Can we combine multiple excel files into one excel file using SSIS? Can we install only SSIS on a machine without installing actual SQL Service can we open sas files in sql server, Can't Aquire connections because OfflineMode is true C...
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...
unique key on varchar(128) as part of the schema. The load took some 3 hours before I aborted it finding out it was just about 20% done. The problem is – unique keys are always rebuilt using key_cache, which means we’re down to some 100-200 rows/sec as soon as index becomes ...
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. ...
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: ...
If we are using MySQL or SQL Server, then we can choose the tinyint column type for the Primary Key column.For instance, if we have a country table that stores all the countries where our customers are located, knowing that there are less than 200 countries in the world, it makes no ...
SQL> select /*ACS_1*/ count(*), max(empno) from emp where deptno = :deptno; COUNT(*) MAX(EMPNO) --- --- 99900 100000 We expect to get the same plan as before for this execution because Oracle initially assumes it can be shared. Let's check: Copy code snippet Copied...