Menu
Since you can't use a calculated column in a where-clause in MySQL like this:
SELECT a,b,c,(a*b+c) AS d FROM table WHERE d > n ORDER by d you have to use
SELECT a,b,c,(a*b+c) AS d FROM table WHERE (a*b+c) > n ORDER by d Is the calculation (in that example "(a*b+c)" executed once per row or twice? Is there a way to make it faster? I find it strange it's possible to ORDER on the column but not to have a WHERE-clause.
347
Some Limitations. You can not reference columns from other tables for a computed column expression directly. You can not apply insert or update statements on computed columns.
Calculated columns in DAX are useful whenever you have to use data from other tables in the data model, or consider aggregated data in a computation. Two examples where the calculated columns are very useful are the Static Segmentation and the ABC Classification patterns.
Go to your database, right click on tables, select “New Table” option. Create all columns that you require and to mark any column as computed, select that column and go to column Properties window and write your formula for computed column.
Get a list of computed columns in a SQL Server database. We can use the system function sys. computed_columns and join it with the sys. objects to get a list of available computed columns, their data type, and the column definition (formula).
You can use HAVING to filter on a computed column:
SELECT a,b,c,(a*b+c) AS d, n FROM table HAVING d > n ORDER by d Note that you need to include n in the SELECT clause for this to work.
115
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
