What causes MULTI_VALUE_SUBQUERY_ERROR?

A subquery in a SELECT list or WHERE = clause that is expected to return one row but returns multiple rows at runtime. A subquery used with `= ` instead of `IN` when the source data has grown to contain duplicates. Missing LIMIT 1 on a lookup subquery. JOIN condition not unique, causing a previously single-row subquery to return multiple rows after a data change

How do I fix MULTI_VALUE_SUBQUERY_ERROR?

Add `LIMIT 1` to the subquery if returning the first match is acceptable. Use an aggregation (MAX, MIN, ANY_VALUE) inside the subquery to collapse multiple rows into one. Change `= (subquery)` to `IN (subquery)` if multiple values are valid matches. Investigate the source data change that caused the subquery to return multiple rows and fix the root cause. Rewrite as a JOIN if the intent is to match all rows rather than a single scalar value

High severityquery

Power BI Refresh Error:
MULTI_VALUE_SUBQUERY_ERROR

What does this error mean?

A scalar subquery (used in a position that expects a single value) returned more than one row. Spark SQL raises this error at runtime when the subquery result set has more than one row.

Common causes

1A subquery in a SELECT list or WHERE = clause that is expected to return one row but returns multiple rows at runtime
2A subquery used with `= ` instead of `IN` when the source data has grown to contain duplicates
3Missing LIMIT 1 on a lookup subquery
4JOIN condition not unique, causing a previously single-row subquery to return multiple rows after a data change

How to fix it

1Add `LIMIT 1` to the subquery if returning the first match is acceptable
2Use an aggregation (MAX, MIN, ANY_VALUE) inside the subquery to collapse multiple rows into one
3Change `= (subquery)` to `IN (subquery)` if multiple values are valid matches
4Investigate the source data change that caused the subquery to return multiple rows and fix the root cause
5Rewrite as a JOIN if the intent is to match all rows rather than a single scalar value

Frequently asked questions

How is this different from UNSUPPORTED_SUBQUERY_EXPRESSION_CATEGORY?

UNSUPPORTED_SUBQUERY_EXPRESSION_CATEGORY is a parse/planning error — Spark rejects the query structure before execution. MULTI_VALUE_SUBQUERY_ERROR is a runtime error — the query is structurally valid but data at execution time violates the scalar constraint.