![]() Notes were based on everyone's great feedback below. Then the Default-Constraint will not be used and NULL will be inserted as the Value. If you insert a Record and Specify SomeCol's value as NULL (and your column allows nulls), If you insert a Record into SomeTable and do not Specify SomeCol's value, then it will Default to 0. How Inserts work with a Default-Constraint: If your Column is NOT NULL, then it will automatically use the Default Valueįor all Existing Records, whether you specify WITH VALUES or not. The WITH VALUES is only needed when your Column is NullableĪnd you want the Default Value used for Existing Records. If you leave out CONSTRAINT D_SomeTable_SomeCol then SQL Server will autogenerateĪ Default-Contraint with a funny Name like: DF_SomeTa_SomeC_4FB7FEF6 WITH VALUES -Add if Column is Nullable and you want the Default Value for Existing Records. I realize having the fields separated which hold different types of data would be preferrable.ĬONSTRAINT ĬONSTRAINT D_SomeTable_SomeCol -When Omitted a Default-Constraint Name is autogenerated.ĭEFAULT (0)-Optional Default-Constraint. ![]() PS: The table design that requires this type of join is not something that I can get changed at this time. This SO question is similar, but it looks like no one provided any concrete answers to the performance difference of these approaches: T-SQL speed comparison between LEFT() vs. I am running this on an IBM iSeries, though would be interested in answers in a general sense to learn more about sql query optimization.ĭoes it make sense that Method 2 would execute faster? Also, the execution plan shows a recommended index for Method 2 that could improve its performance. ![]() The query execution plan has a lot less steps using Method 1 compared to Method 2, however, it looks like Method 2 executes much faster. Method 2: ON substr(tB.columnB,1,2) = tA.columnA Method 1: ON tB.columnB like tA.columnA || '%' I have developed 2 different statements to handle this and I have tried to analyze the performance of each method. I need to join columnA from tableA to the first 2 characters of columnB from tableB. I am working on a join condition between 2 tables where one of the columns to match on is a concatentation of values. ![]()
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