mysql - 如何从mysql文档中理解 "not necessarily to DML statements"？

Question

http://dev.mysql.com/doc/refman/5.5/en/innodb-consistent-read.html

Note
The snapshot of the database state applies to SELECT statements within a transaction, not necessarily to DML statements. If you insert or modify some rows and then commit that transaction, a DELETE or UPDATE statement issued from another concurrent REPEATABLE READ transaction could affect those just-committed rows, even though the session could not query them. If a transaction does update or delete rows committed by a different transaction, those changes do become visible to the current transaction. For example, you might encounter a situation like the following:

SELECT COUNT(c1) FROM t1 WHERE c1 = 'xyz'; -- Returns 0: no rows match.
DELETE FROM t1 WHERE c1 = 'xyz'; -- Deletes several rows recently committed by other transaction.

SELECT COUNT(c2) FROM t1 WHERE c2 = 'abc'; -- Returns 0: no rows match.
UPDATE t1 SET c2 = 'cba' WHERE c2 = 'abc'; -- Affects 10 rows: another txn just committed 10 rows with 'abc' values.
SELECT COUNT(c2) FROM t1 WHERE c2 = 'cba'; -- Returns 10: this txn can now see the rows it just updated.

Answer 1

来自Glossary :

DML
Data manipulation language, a set of SQL statements for performing insert, update, and delete operations.

换句话说，它们是修改表中数据的 SQL 语句，而不是像 SELECT 那样仅检索数据。

该段落的意思是，如下面的示例所示，修改查询可能会影响在另一个事务中提交的行，即使这是在您启动当前事务之后发生的。当这种情况发生时，您的事务快照将更新以包含这些行。