louislam/uptime-kuma · error · Error

Multiple columns were found, expected only one value

Error message

Multiple columns were found, expected only one value

What it means

Thrown by mssqlQuerySingleValue when the first row exposes more than one column. The single-value path requires a 1-row x 1-column result so the condition evaluator receives an unambiguous scalar.

Source

Thrown at server/monitor-types/mssql.js:117

            await pool.connect();
            const result = await pool.request().query(query);

            // Check if we have results
            if (!result.recordset || result.recordset.length === 0) {
                throw new Error("Query returned no results");
            }

            // Check if we have multiple rows
            if (result.recordset.length > 1) {
                throw new Error("Multiple values were found, expected only one value");
            }

            const firstRow = result.recordset[0];
            const columnNames = Object.keys(firstRow);

            // Check if we have multiple columns
            if (columnNames.length > 1) {
                throw new Error("Multiple columns were found, expected only one value");
            }

            // Return the single value from the first (and only) column
            return firstRow[columnNames[0]];
        } catch (err) {
            log.debug("sqlserver", "Error caught in the query execution.", err.message);
            throw err;
        } finally {
            if (pool) {
                await pool.close();
            }
        }
    }
}

module.exports = {
    MssqlMonitorType,
};

View on GitHub (pinned to 6b5ea01557)

Solutions

1. Project exactly one column: SELECT <col> FROM ....
2. If you need several fields, aggregate them into one expression (CONCAT, JSON, computed column).
3. Drop unused columns from the SELECT list.

Example fix

-- before: SELECT id, balance FROM accounts WHERE id=@id;
-- after:  SELECT balance FROM accounts WHERE id=@id;

function columnCountOfFirstRow(r) { return r?.recordset?.[0] ? Object.keys(r.recordset[0]).length : 0; }

function isSingleColumn(r) { return r?.recordset?.length>=1 && Object.keys(r.recordset[0]).length === 1; }

When it happens

Trigger: monitor.conditions non-empty, exactly one row returned, but Object.keys(firstRow).length > 1. Happens with SELECT *, multi-column projections, or queries that include computed/identity columns.

Common situations: SELECT * used for convenience; query selects id plus the value column; a view returns extra metadata columns.

Related errors

• Query returned no results
• Multiple values were found, expected only one value
• Query result did not meet the specified conditions (${result
• Database connection/query failed: ${error.message}
• Query returned no results

AI-assisted analysis of louislam/uptime-kuma@6b5ea01557 (2026-08-12). Data as JSON: /api/errors/88212fddeb70e47b. Report an issue: GitHub.