Absolute value for column in Python
Use pandas.DataFrame.abs(). import pandas as pd df = pd.DataFrame(data={‘count’:[1, -1, 2, -2, 3, -3]}) df[‘count’] = df[‘count’].abs() print(df) count #0 1 #1 1 #2 2 #3 2 #4 3 #5 3
calculated-columns
How can I alter this computed column in SQL Server 2008?
Something like this: ALTER TABLE dbo.MyTable DROP COLUMN OldComputedColumn ALTER TABLE dbo.MyTable ADD OldComputedColumn AS OtherColumn + 10 Source
formula for computed column based on different table’s column
You could create a user-defined function for this: CREATE FUNCTION dbo.GetValue(@ncode INT, @recid INT) RETURNS INT AS SELECT @recid * nvalue FROM c_const WHERE code = @ncode and then use that to define your computed column: ALTER TABLE dbo.YourTable ADD NewColumnName AS dbo.GetValue(ncodeValue, recIdValue)
Calculated column in EF Code First
You can create computed columns in your database tables. In the EF model you just annotate the corresponding properties with the DatabaseGenerated attribute: [DatabaseGenerated(DatabaseGeneratedOption.Computed)] public double Summ { get; private set; } Or with fluent mapping: modelBuilder.Entity<Income>().Property(t => t.Summ) .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Computed) As suggested by Matija Grcic and in a comment, it’s a good idea to make … Read more
Sql Server deterministic user-defined function
You just need to create it with schemabinding. SQL Server will then verify whether or not it meets the criteria to be considered as deterministic (which it does as it doesn’t access any external tables or use non deterministic functions such as getdate()). You can verify that it worked with SELECT OBJECTPROPERTY(OBJECT_ID(‘[dbo].[FullNameLastFirst]’), ‘IsDeterministic’) Adding the … Read more
SQL Server String Concatenation with Null
You can use ISNULL(….) SET @Concatenated = ISNULL(@Column1, ”) + ISNULL(@Column2, ”) If the value of the column/expression is indeed NULL, then the second value specified (here: empty string) will be used instead.
TSQL divide by zero encountered despite no columns containing 0
SQL is a declarative language; you write a query that logically describes the result you want, but it is up to the optimizer to produce a physical plan. This physical plan may not bear much relation to the written form of the query, because the optimizer does not simply reorder ‘steps’ derived from the textual … Read more
The condition has length > 1 and only the first element will be used
You get the error because if can only evaluate a logical vector of length 1. Maybe you miss the difference between & (|) and && (||). The shorter version works element-wise and the longer version uses only the first element of each vector, e.g.: c(TRUE, TRUE) & c(TRUE, FALSE) # [1] TRUE FALSE # c(TRUE, … Read more
PostgreSQL: using a calculated column in the same query
You need to wrap the SELECT statement into a derived table in order to be able to access the column alias: select cost1, quantity_1, cost_2, quantity_2 total_1 + total_2 as total_3 from ( select cost_1, quantity_1, cost_2, quantity_2, (cost_1 * quantity_1) as total_1, (cost_2 * quantity_2) as total_2 from data ) t There won’t be … Read more
How can one work fully generically in data.table in R with column names in variables
Problem you are describing is not strictly related to data.table. Complex queries cannot be easily translated to code that machine can parse, thus we are not able to escape complexity in writing a query for complex operations. You can try to imagine how to programmatically construct a query for the following data.table query using dplyr … Read more