Column width.  Attempting to create an index on an NDB table column whose width is greater than 3072 bytes is rejected with ER_TOO_LONG_KEY: Specified key was too long; max key length is 3072 bytes.

Attempting to create an index on an NDB table column whose width is greater than 3056 bytes succeeds with a warning. In such cases, statistical information is not generated, which means a nonoptimal execution plan may be selected. For this reason, you should consider making the index length shorter than 3056 bytes if possible.

TEXT and BLOB columns.  You cannot create indexes on NDB table columns that use any of the TEXT or BLOB data types.

FULLTEXT indexes.  The NDB storage engine does not support FULLTEXT indexes, which are possible for MyISAM and InnoDB tables only.

However, you can create indexes on VARCHAR columns of NDB tables.

USING HASH keys and NULL.  Using nullable columns in unique keys and primary keys means that queries using these columns are handled as full table scans. To work around this issue, make the column NOT NULL, or re-create the index without the USING HASH option.

Prefixes.  There are no prefix indexes; only entire columns can be indexed. (The size of an NDB column index is always the same as the width of the column in bytes, up to and including 3072 bytes, as described earlier in this section. Also see Section 25.2.7.6, “Unsupported or Missing Features in NDB Cluster”, for additional information.)

BIT columns.  A BIT column cannot be a primary key, unique key, or index, nor can it be part of a composite primary key, unique key, or index.

AUTO_INCREMENT columns.  Like other MySQL storage engines, the NDB storage engine can handle a maximum of one AUTO_INCREMENT column per table, and this column must be indexed. However, in the case of an NDB table with no explicit primary key, an AUTO_INCREMENT column is automatically defined and used as a “hidden” primary key. For this reason, you cannot create an NDB table having an AUTO_INCREMENT column and no explicit primary key.

The following CREATE TABLE statements do not work, as shown here:

# No index on AUTO_INCREMENT column; table has no primary key
# Raises ER_WRONG_AUTO_KEY
mysql> CREATE TABLE n (
    ->     a INT,
    ->     b INT AUTO_INCREMENT
    ->     )
    -> ENGINE=NDB;
ERROR 1075 (42000): Incorrect table definition; there can be only one auto
column and it must be defined as a key 

# Index on AUTO_INCREMENT column; table has no primary key
# Raises NDB error 4335
mysql> CREATE TABLE n (
    ->     a INT,
    ->     b INT AUTO_INCREMENT,
    ->     KEY k (b)
    ->     )
    -> ENGINE=NDB;
ERROR 1296 (HY000): Got error 4335 'Only one autoincrement column allowed per
table. Having a table without primary key uses an autoincr' from NDBCLUSTER

The following statement creates a table with a primary key, an AUTO_INCREMENT column, and an index on this column, and succeeds:

# Index on AUTO_INCREMENT column; table has a primary key
mysql> CREATE TABLE n (
    ->     a INT PRIMARY KEY,
    ->     b INT AUTO_INCREMENT,
    ->     KEY k (b)
    ->     )
    -> ENGINE=NDB;
Query OK, 0 rows affected (0.38 sec)

Every column referenced as a foreign key requires an explicit unique key, if it is not the table's primary key.

ON UPDATE CASCADE is not supported when the reference is to the parent table's primary key.

This is because an update of a primary key is implemented as a delete of the old row (containing the old primary key) plus an insert of the new row (with a new primary key). This is not visible to the NDB kernel, which views these two rows as being the same, and thus has no way of knowing that this update should be cascaded.

ON DELETE CASCADE is also not supported where the child table contains one or more columns of any of the TEXT or BLOB types. (Bug #89511, Bug #27484882)

SET DEFAULT is not supported. (Also not supported by InnoDB.)

The NO ACTION keyword is accepted but treated as RESTRICT. NO ACTION, which is a standard SQL keyword, is the default in MySQL 9.5. (Also the same as with InnoDB.)

In earlier versions of NDB Cluster, when creating a table with foreign key referencing an index in another table, it sometimes appeared possible to create the foreign key even if the order of the columns in the indexes did not match, due to the fact that an appropriate error was not always returned internally. A partial fix for this issue improved the error used internally to work in most cases; however, it remains possible for this situation to occur in the event that the parent index is a unique index. (Bug #18094360)