|| (pipe pipe sign) operator
Applies to: 
Databricks SQL Databricks Runtime
Returns the concatenation of expr1 and expr2. This operator is a synonym for concat function.
Syntax
expr1 || expr2
Arguments
expr1: A STRING, BINARY or ARRAY of STRING or BINARY expression.expr2: An expression with type matchingexpr1.
Returns
The result type matches the argument types.
Examples
SQL
> SELECT 'Spark' || 'SQL';
SparkSQL
> SELECT array(1, 2, 3) || array(4, 5) || array(6);
[1,2,3,4,5,6]