"no such table" / relation does not exist

The table name in your query doesn't match what the database actually has — usually a typo, the wrong schema, or a case-sensitivity trap. Here's how to find out which.

• SQLite: no such table: custmers
• PostgreSQL: ERROR: relation "custmers" does not exist
• MySQL: Table 'mydb.custmers' doesn't exist
• SQL Server: Invalid object name 'custmers'.

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The cause, roughly in order of likelihood

1. Typo in the table name. By far the most common cause — check the exact spelling and pluralization (customer vs customers) against your actual schema.
2. Wrong schema or database. orders might really exist, just as sales.orders or public.orders — not bare orders in whatever schema your connection defaults to. Postgres and SQL Server both search a default schema path unless you qualify the name.
3. Case sensitivity. Postgres folds unquoted identifiers to lowercase, so a table created as "Customers" (quoted, mixed case) can only be referenced as "Customers" afterward — bare customers genuinely won't find it. MySQL's sensitivity depends on the OS and a server setting. SQL Server and SQLite are case-insensitive by default for identifiers.
4. It's a view, and the view's own query is broken, so the view itself failed to resolve — the error points at the outer table name but the real problem is one level down.
5. You're connected to the wrong database entirely (right table name, wrong environment) — worth a sanity check before anything else if the table should obviously exist.

How to check what's actually there

Rather than guessing, list what the database thinks exists:

-- PostgreSQL
SELECT table_schema, table_name FROM information_schema.tables
WHERE table_name ILIKE '%custom%';

-- MySQL
SHOW TABLES LIKE '%custom%';

-- SQL Server
SELECT schema_name(schema_id), name FROM sys.tables WHERE name LIKE '%custom%';

-- SQLite
SELECT name FROM sqlite_master WHERE type = 'table' AND name LIKE '%custom%';

The correctly-spelled, correctly-schema'd query runs fine:

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