vpruthi/doc-exports
1
0
Fork 0
forked from docs/doc-exports
Code Pull Requests Activity
doc-exports/docs/ddm/umn/ddm_08_0009.html
Ru, Li Yi 4b09a03a51 ddm_umn 
Reviewed-by: Wagner, Fabian <fabian.wagner@t-systems.com>
Co-authored-by: Ru, Li Yi <liyiru7@huawei.com>
Co-committed-by: Ru, Li Yi <liyiru7@huawei.com>
2024-04-11 11:39:26 +00:00

2.5 KiB
Raw Permalink Blame History

UPDATE

Common Syntax

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

Syntax Restrictions

  • 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