All columns and data values in Sigma have a value type. A column or value's data type governs how it is displayed and what operations can be performed on it.
Summary of Content
Sigma's Value Types
Possible value types include text, dates, numbers, logical (true/false), variant and null.
Dates in Sigma can represent either a specific calendar date or a specific date and time.
Null represents the absence of value. In the worksheet Null is displayed as an empty cell. Null values can appear anywhere for a number of reasons:
- Null values were already present in the linked database table
- A formula could not compute a value, like 100 / 0
- A corresponding row could not be found in a joined table
In many cases passing a Null to a function which is not expecting it will cause a Null result. This can lead to some odd results:
3 = 3 // True
3 = 1 // False
3 = Null // Null
Null = Null // Null
This behavior helps Sigma to continue in spite of what would otherwise be an error, at the expense of sometimes obscuring the source of the error. In cases where a possible Null value is expected, functions like IsNull and Coalesce can be helpful.
As is the case for all values, you may choose to filter Null data from your worksheet or dashboard on a per column basis.
Most data warehouses support some form of composite data within columns. (e.g. nested arrays, nested structures, JSON or XML) Sigma refers to these as variants. Sigma gives you an interactive visual interface to extract columns of data from variant columns. To extract data from a variant column open the column's menu and choose Extract Columns. Learn more.
Value Types in Sigma and your Database
Data warehouses have their own library of system supported value types. These types are intended for optimal data storage and may be very complex. When your connected warehouse data is queried by Sigma, we consolidate these database types into Sigma's simplified value types.
If a database table contains a type that doesn’t correspond to one of Sigma’s own, Sigma will treat its values as text.
Functions and Types
Each function and operator has rules about the types of arguments it allows. If an argument does not match the acceptable input type, the formula editor will display a warning and the column will be in an error state.
Sigma's function documentation will indicate if there are restrictions to argument types for the given function. See function index.
Sometimes a value will not be recognized as the correct type, or a formula will require that you specify its type. Use an appropriate type-conversion function to ensure the data is treated as the correct Type. Learn how.