SQL error messages explained
Paste the error your database gave you, or scan the list below. Each page shows the failing query, runs it in your browser, and explains what the database is telling you.
- Fix “Column Must Appear in the GROUP BY Clause” in SQL
A selected column is neither grouped nor aggregated, so there is no single value to show.
must appear in the GROUP BY clause - Fix “Column Not Found” When Filtering on a SQL Alias
WHERE runs before SELECT assigns aliases, so the alias does not exist yet.
does not exist - Fix “Ambiguous Column Reference” in a SQL JOIN
Both joined tables have that column name, so the database refuses to guess.
ambiguous - Fix “Aggregate Functions Are Not Allowed in WHERE” in SQL
WHERE filters rows before grouping, so aggregates do not exist yet. Use HAVING.
aggregates - Fix “Window Functions Are Not Allowed in WHERE” in SQL
Window functions run after WHERE, so you cannot filter on one directly.
window function - Fix “Failing Row Contains” Constraint Errors in SQL
An INSERT, UPDATE, or DELETE broke a rule on the table. The detail line names the row.
Failing row contains - Fix “NOT NULL Constraint Failed” in SQL
A required column got no value. Supply one, give the column a default, or let it be null.
NOT NULL constraint failed - Fix “Duplicate Key Violates Primary Key Constraint” in SQL
The key you are inserting already exists. Find the existing row before you write.
violates primary key constraint - Fix “Violates Foreign Key Constraint” in SQL
A child row points at a parent that is not there, or a parent still has children.
foreign key constraint - Fix “CHECK Constraint Failed” in SQL
A value is storable but breaks a business rule the table enforces. Read the expression.
CHECK constraint failed - Fix “Cannot Insert Into a Generated Column” in SQL
A generated column computes itself. Leave it out of the column list entirely.
Cannot insert into a generated column - Fix “Is of Type View, Trying to Drop Type Table” in SQL
DROP TABLE will not remove a view, and IF EXISTS does not rescue it. Drop the type you made.
trying to drop type Table - Fix “Syntax Error at or Near” in SQL
The parser stopped at the first word it could not use. The quoted token is where it gave up, not always where the mistake is.
syntax error at or near - Fix “Referenced Column Not Found” in SQL
No table in the FROM clause has a column by that name. Usually a typo or a table you did not join.
not found in FROM clause - Fix “Different Number of Columns” in a SQL UNION
Each SELECT in a UNION has to return the same number of columns, in the same order.
different number of columns
Other errors you will meet
These come up often enough to cover here, even without a dedicated page yet.
Referenced column ... not found
The column name is misspelled, lives in a different table, or needs a table alias. Check it against the schema, and qualify it (c.customer_id) when more than one table is in play.
Syntax error near ...
Something is malformed at that spot. The usual culprits: a missing comma between selected columns, an unclosed quote or parenthesis, or a misspelled keyword. The error points to where parsing broke, which is often right after the real mistake.
No function matches the given name and argument types
A type mismatch, often from comparing text to a number or passing a string where a date is expected. Cast explicitly withCAST(x AS INTEGER) or fix the literal's quotes.
Conversion error / could not convert
A value could not be coerced to the needed type, for example the text'N/A' in a numeric column. Filter or clean the bad values first, or guard withTRY_CAST (DuckDB), which returns NULL instead of failing.
If the query runs without complaint and comes back empty, there is nothing here to decode: it succeeded. Readwhy a query runs but returns no rows instead.
When you get stuck on any of these, rebuild the query in small steps. Start withSELECT * FROM table, add one join, then one filter, checking the result after each change.