Data Query Language

只读的查询数据被独立称为 DQL，但数据查询通常被认为是 DML 中的一部分。纯 SELECT 数据时语句是 DQL；添加 FROM 和 WHERE 操作符后可以认为语句是 DML。

Data query language (DQL) is part of the base grouping of SQL sub-languages. DQL statements are used for performing queries on the data within schema objects. The purpose of DQL commands is to get the schema relation based on the query passed to it.
Although often considered part of DML, the SQL SELECT statement is strictly speaking an example of DQL. When adding FROM or WHERE data manipulators to the SELECT statement the statement is then considered part of the DML. ^[1]