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INSERT

Inserts data into a table.

Syntax

INSERT [IGNORE] [INTO] tbl_name [(col_name,...)]
    [VALUES | VALUE] (expr,...),(...),...
    [ ON DUPLICATE KEY UPDATE
      col_name = insert_expr
        [, col_name = insert_expr] ... ]

INSERT [IGNORE] [INTO] tbl_name [(col_name,...)]
    SELECT [WITH(force_random_reshuffle=1)] ...
    [ ON DUPLICATE KEY UPDATE
      col_name = insert_expr
        [, col_name = insert_expr] ... ]

INSERT [IGNORE] [INTO] tbl_name
    SET col_name=expr, ...
    [ ON DUPLICATE KEY UPDATE
      col_name = insert_expr
        [, col_name = insert_expr] ... ]

 insert_expr:
      expr
    | VALUES(col_name)

Remarks

  • The first field of type TIMESTAMP or TIMESTAMP(6) has special behavior for insert operations, defaulting to the current timestamp value. Refer to the discussion of these types in the Data Types topic for more details. In addition, a field f declared with the DEFAULT <value> modifier will be set to <value> if no explicit value for f is set.
  • MemSQL supports constants, DEFAULT, or nullary builtins such as NOW(), RAND(), or UNIX_TIMESTAMP() for expressions (expr) for INSERTs.
  • INSERT queries will fail if the maximum_table_memory limit has been reached. See /admin/memory_limits_include for more information.
  • Non-local (cross-shard and sharded->reference) INSERT ... SELECT queries that are not the first statement of a transaction are not supported.
  • INSERT IGNORE disables transactions for multi-INSERT. In this case, MemSQL will ignore records with duplicate keys and, without rolling back, continue inserting records with unique keys. This can speed up performance of multi-INSERT because it avoids an extra roundtrip between the aggregators and leaves.
  • Multi-inserts are atomic in nature. For a multi-insert transaction, either all the rows are committed or the transaction is rolled back.
  • Multi-inserts may or may not have consecutive AUTO_INCREMENT values. See AUTO_INCREMENT behavior for more information.
  • When you use the IGNORE modifier, data conversion errors for a row being inserted are ignored, and the row will be inserted with default values for fields where the conversion failed.
  • If the ON DUPLICATE KEY UPDATE clause is specified, and a row is to be inserted that would result in a duplicate value in a PRIMARY KEY or UNIQUE index, MemSQL will instead perform an UPDATE of the old row.
  • The IGNORE modifier and ON DUPLICATE KEY UPDATE clause cannot be used in the same INSERT query, because their semantics contradict each other. For more information, see Query Errors
  • When using ON DUPLICATE KEY UPDATE, the affected row count will be 0 if no existing row is changed, 1 if a new row is inserted, and 2 if an existing row is updated.
  • ON DUPLICATE KEY UPDATE cannot update unique key columns in columnstore tables.
  • This command must be run on the master aggregator or a child aggregator node (see Node Requirements for MemSQL Commands). Note that when running this command on reference tables you must connect to the master aggregator.
  • INSERT ... SELECT into AUTO_INCREMENT columns can only be pushed down to leaves if the source column is also AUTO_INCREMENT, because AUTO_INCREMENT values are generated on the aggregator. This prevents insertion of 0 or NULL values in the AUTO_INCREMENT column, if the source column isn’t AUTO_INCREMENT. For more information, see AUTO_INCREMENT Behavior.
  • Writing to multiple databases in a transaction is not supported.

force_random_reshuffle

To reduce skew, you can force the INSERT … SELECT to redistribute the data with the force_random_reshuffle query hint. A common use case for this hint is on keylessly sharded tables, as it allows forced redistribution of data among partitions, rather than inserting it locally into the same partition.

ON DUPLICATE KEY UPDATE

ON DUPLICATE KEY UPDATE allows you to perform an upsert of a row. For more information, see the Performing Upserts topic.

Examples

Simple Insert

INSERT INTO mytbl (v) VALUES ("hello"), ("goodbye");

This example shows a successful insert even when converting a NULL value to an int NOT NULL type, with the NULL replaced by 0:

memsql> CREATE TABLE mytbl2(a int not null);
Query OK, 0 rows affected (0.72 sec)

memsql> INSERT IGNORE mytbl2 VALUES(null);
Query OK, 1 row affected (0.18 sec)

memsql> SELECT * FROM mytbl2;
+---+
| a |
+---+
| 0 |
+---+
1 row in set (0.24 sec)

ON DUPLICATE KEY UPDATE and force_random_reshuffle

This example shows a simple INSERT with both ON DUPLICATE KEY UPDATE and force_random_reshuffle. The rows from mytbl_new will be inserted into mytbl, and distributed across partitions.

memsql> INSERT INTO mytbl (column1, column2, column3)
    SELECT WITH(force_random_reshuffle=1)
    * FROM mytbl_new ON DUPLICATE KEY UPDATE
      column1 = VALUES(column1),
      column2 = VALUES(column2),
      column3 = VALUES(column3);
****
Query OK, 29 rows affected (0.18 sec)

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