Type mismatch occurs when an expression’s data type differs from the column, variable, or parameter it’s assigned to.
Type mismatch error means the data type of a value doesn’t match the destination column or variable. Align data types or explicitly CAST/CONVERT the value to resolve the mismatch.
ERROR: column "price" is of type numeric but expression is of type text
Type mismatch errors surface when the database engine detects that a literal, column, or variable has an incompatible data type for the current operation. The engine stops execution to prevent corrupt or ambiguous data.
Developers see this error during INSERT, UPDATE, SELECT with UNION, or function calls where operands differ in type. Fixing it quickly protects data integrity and avoids application downtime.
Mismatched column and literal types trigger the error most often.
Example: inserting text '123' into an INTEGER column without casting.
Implicit conversions fail when the target type cannot safely accept the source type, such as assigning VARCHAR to NUMERIC in strict SQL modes.
JOINs or UNIONs with differently typed columns also raise type mismatch because the engine cannot decide a common type.
Align every value with its target data type before execution.
This may require schema changes, explicit CAST/CONVERT, or parameter typing in client code.
Validate incoming data in application logic to ensure numbers, dates, and booleans are sent in the correct format.
Text-to-Numeric: Use CAST('123' AS INTEGER) or parameterize with integer type to satisfy integer columns.
String-to-Date: Apply TO_DATE('2024-06-01','YYYY-MM-DD') or CAST('2024-06-01' AS DATE).
Union Columns: Wrap operands with a common type, e.g., SELECT col::TEXT ...
UNION SELECT other_col::TEXT.
Define strict schemas with precise data types and avoid generic VARCHAR unless necessary.
Document each column’s expected format.
Parameterize SQL in your application so the driver sends typed parameters rather than raw strings.
Employ continuous integration tests that run representative queries against a staging database to detect mismatches early.
“Cannot cast type” errors appear when CAST/CONVERT is impossible; verify values fit the target domain.
“Datatype mismatch in criteria expression” in MS Access is analogous; check form inputs and use CInt(), CDate(), or CLng().
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Run the failing query with EXPLAIN or review the full error text; most engines state the column name and expected type.
Avoid disabling checks; instead CAST values. Some engines allow relaxed modes, but this risks silent data loss.
Performance difference is negligible; choose the function idiomatic to your database (CAST in ANSI SQL, CONVERT in SQL Server).
Galaxy’s AI Copilot highlights datatype mismatches in real time and suggests correct CAST/CONVERT syntax before you run the query.
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