"Column count doesn't match value count"

The number of values in your INSERT doesn't match the number of columns — either the column list, or a row in a multi-row VALUES list, is short or long by one.

• SQLite: 3 values for 2 columns
• PostgreSQL: ERROR: INSERT has more expressions than target columns (or the reverse: INSERT has more target columns than expressions)
• MySQL: Column count doesn't match value count at row 1
• SQL Server: Column name or number of supplied values does not match table definition.

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Two columns named, three values given.

The two directions

Too many values — an extra column crept into the VALUES list that isn't in the column list (shown above), often from copy-pasting a row template from a table with more columns.

Too few values — a column was added to the column list (or to the table, when no column list is given at all) but an existing VALUES row wasn't updated to match:

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Where this bites hardest: multi-row INSERT

A single-row mistake fails immediately and obviously. The same typo in one row of a 50-row VALUES list still fails the whole statement — which is the good outcome. The genuinely dangerous version is a generated INSERT, where a template string is built per row in application code and one row's data happens to be missing a field (a NULL/undefined value that got dropped instead of included as NULL) — that produces this exact error, but only for the one malformed row buried among otherwise-correct ones, making it look like a data problem rather than the query-generation bug it actually is.

The fix

Count columns against values explicitly rather than eyeballing it — and prefer always naming the column list explicitly, even when inserting into every column, so a later ALTER TABLE ADD COLUMN doesn't silently change what a bare INSERT INTO t VALUES (...) means:

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