Understanding the 'Concatenation Operator' in SQL and BigQuery

Summary

The '||' symbol in SQL, also known as the concatenation operator, is used to combine things. It's the ANSI SQL standard concatenation operator, theoretically working across database engines, but some, like SQLServer, use '+' for string concatenation. In BigQuery, '||' functions similarly to CONCAT() for STRINGs and ARRAY_CONCAT() for ARRAYs.