MySQL throws ER_NULL_COLUMN_IN_INDEX when you try to create or alter an index that references a column declared NULLABLE with a storage engine that forbids NULLs in indexed columns.
MySQL Error 1121: ER_NULL_COLUMN_IN_INDEX occurs when an index includes a column that allows NULLs but the table handler (usually InnoDB with a FULLTEXT or older MyISAM engine) prohibits NULL values in indexed fields. Change the column to NOT NULL or drop NULLs before indexing to resolve.
Table handler doesn't support NULL in given index. Please
Error 1121 signals that the selected storage engine cannot store NULL values in a column that is part of an index. MySQL halts the CREATE INDEX or ALTER TABLE operation to protect index integrity.
The message surfaces during ALTER TABLE, CREATE TABLE, or CREATE INDEX commands when at least one indexed column is nullable.
It can also arise during table import or replication if the target schema differs.
Indexes rely on predictable, comparable values. NULL breaks ordering guarantees for some engines, leading to corrupt lookups or crashes. Fixing the definition guarantees deterministic query plans and safer migrations.
Incorrect column definitions with NULL allowed is the primary trigger.
Storage engines like MyISAM, some MEMORY versions, and ndbcluster disallow NULL in indexed columns.
Convert the column to NOT NULL, supply a default value, or switch to a handler that permits nullable indexes such as InnoDB (non-FULLTEXT). Alternatively, drop the column from the index.
During schema migration, scripted DDL often forgets to add NOT NULL. Adding a NOT NULL constraint and repopulating data clears the error.
In legacy schemas, removing historical NULLs and adding defaults makes the index build succeed.
Define business-critical indexed columns as NOT NULL from the beginning. Use Galaxy’s linting to surface nullable index definitions before deployment. Automate schema checks in CI pipelines.
Errors 1280 (ER_DROP_INDEX_FK) and 1061 (ER_DUP_KEYNAME) frequently accompany index refactors. They require adjusting foreign keys or renaming conflicting indexes once NULL constraints are handled.
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Only if the storage engine supports it. InnoDB permits NULLs in regular indexes, but MyISAM and MEMORY do not.
Yes. Updating existing NULLs and altering the column to NOT NULL with a default resolves the issue.
Galaxy’s schema-aware linting flags any attempt to create an index on a nullable column, preventing the error before deployment.
NOT NULL often improves performance because the engine avoids additional NULL checks during index scans.
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