concat function
Applies to: 
Databricks SQL Databricks Runtime
Returns the concatenation of the arguments. This function is a synonym for || (pipe pipe sign) operator.
Syntax
concat(expr1, expr2 [, ...] )
Arguments
exprN: Expressions which are all STRING, all BINARY or all ARRAYs of STRING or BINARY.
Returns
The result type matches the argument types.
There must be at least one argument.
Examples
SQL
> SELECT concat('Spark', 'SQL');
SparkSQL
> SELECT concat(array(1, 2, 3), array(4, 5), array(6));
[1,2,3,4,5,6]