UPDATE

UPDATE table_reference
SET col_name1={expr1} [, col_name2={expr2}] ...
[WHERE where_condition]

Subqueries are not supported, including correlated and non-correlated subqueries.
Cross-shard subquery is not supported.
The WHERE condition in the UPDATE statement does not support arithmetic expressions and their subqueries.
Modifying broadcast tables is not supported during an update of multiple tables. (Data in columns of a broadcast table cannot be on the left of SET assignment statements).
Updating the sharding key field of a logical table is not supported because this operation may cause data redistribution.
Setting datetime to 1582 or any value smaller in UPDATE statements is not supported.
UPDATE cannot be used to update sharding key value DEFAULT.
Repeatedly updating the same field in an UPDATE statement is not supported.
Updating a sharding key using UPDATE JOIN syntax is not supported.
UPDATE cannot be used to update self-joins.
Referencing other object columns in assignment statements or expressions may cause unexpected update results. Example:
update tbl_1 a,tbl_2 b set a.name=concat(b.name,'aaaa'),b.name=concat(a.name,'bbbb') on a.id=b.id
UPDATE JOIN supports only joins with WHERE conditions.

Parent topic: DML