String Functions (Transact-SQL)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Azure Synapse Analytics
Analytics Platform System (PDW)
SQL analytics endpoint in Microsoft Fabric
Warehouse in Microsoft Fabric
The following scalar functions perform an operation on a string input value and return a string or numeric value:
All built-in string functions except FORMAT are deterministic. This means they return the same value any time they are called with a specific set of input values. For more information about function determinism, see Deterministic and Nondeterministic Functions.
When string functions are passed arguments that are not string values, the input type is implicitly converted to a text data type. For more information, see Data Type Conversion (Database Engine).