3154
MySQLERRORNotableJSONHIGH confidence
JSON_TABLE: scalar value expected for column
Production Risk
Low — query fails at runtime; restructure the JSON_TABLE definition.
What this means
A JSON_TABLE column that expects a scalar value (for a regular column definition) received a JSON array or object, which cannot be automatically converted to the declared SQL type.
Why it happens
- 1The JSON path for a non-NESTED PATH column points to an array or object instead of a scalar.
How to reproduce
trigger — this will error
trigger — this will error
SELECT jt.* FROM JSON_TABLE('[{"a":[1,2,3]}]', '$[*]' COLUMNS(val INT PATH '$.a')) AS jt;expected output
ERROR 3154 (HY000): JSON_TABLE: Scalar expected, array found.
Fix
Use NESTED PATH for array values
Use NESTED PATH for array values
SELECT jt.* FROM JSON_TABLE('[{"a":[1,2,3]}]', '$[*]' COLUMNS(NESTED PATH '$.a[*]' COLUMNS(val INT PATH '#x27;))) AS jt;Why this works
NESTED PATH expands array elements into multiple rows.
What not to do
✕
Sources
Official documentation ↗
MySQL 8.0 — 3154 ER_JSON_TABLE_SCALAR_EXPECTED
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