Bigquery Error: No matching signature for function CONCAT for argument types. Supported signatures: CONCAT

When you try to concatenate two columns in Bigquery, you might stumble on the below error message:

Error: No matching signature for function CONCAT for argument types: 
FLOAT64, FLOAT64. Supported signatures: CONCAT(STRING, [STRING, ...]); 
CONCAT(BYTES, [BYTES, ...]).

Solution:

CONCAT function can only be used to concatenate two STRING columns. If your column is of other datatypes (DATE / INT64 / FLOAT64 / ...) you will need to first cast them to string for the CONCAT to work. Like shown in the below example:

SELECT CONCAT(CAST(column1 as string), CAST(column2 as string)) as New_Column
FROM tablename

CONCAT function can be used to join two string fields in BigQuery

nVector

posted on 12 Aug 20