这个语句在示例中表示为子查询s1。
This statement is represented in the example as subquery S1.
主查询要求，子查询指定子元素的属性。
The main query asks for; the subquery specifies properties of child.
视图不需要包含子查询。
当这条语句执行的时候,子查询会先执行.
When this statement is executed, the subquery is evaluated first.
一些报表执行需要执行子查询。
映射子查询和聚合功能
从语法上来说,子查询被包含在圆括号中.
Syntactically, subqueries are enclosed within parentheses. For example, the following SELECT statement contains a simple subquery in its WHERE clause
子查询选择列表中没有足够的列。
不能在子查询中使用一个外部表。
这些子查询被称作派生表或表表达式。
These sub queries are called derived tables or table expressions.
子查询是被包含在一组圆括号里执行的。
A subquery is executed by enclosing it in a set of parentheses.
我们直接将两个表连接在一起，而不再使用子查询。
内部子查询是相关子查询。
说明如何通过使用子查询检索相关数据。
Describes how to retrieve related data by using a sub-query.
每一个sggrep命令可以同时指定主查询和子查询。
Each sggrep command can specify both the main query and a subquery.
有两种类型的子查询： 不相关的和相关的。
There are two types of subqueries, uncorrelated and correlated.
重要的是要注意在技术上这不是一个联接，而是一个子查询。
It's important to note that technically, this is not a join, but a subquery.
子查询的属性是什么，有哪些不同类型的子查询？
第二个和后续的参数为字符串，它们被当作子查询。
The second and subsequent arguments are strings, which are treated as sub-queries.
当使用的子查询中包含一个不存在的属性时的更友好的错误信息。
Better error message when using a subquery that contains a reference to non existing property.
如您所见，优化器创建了一个虚拟表来处理in列表子查询。
As you can see, the optimizer creates a virtual table to process the IN-list sub-query.
在此上下文中不允许使用子查询。只允许使用标量表达式。
Subqueries are not allowed in this context. Only scalar expressions are allowed.
在这个示例中，这由最外层的选择语句表示，这个语句将S1用作子查询。
In the example, this is represented by the outermost select statement, which USES S1 as a subquery.
要使用表子查询，需要使用SQL操作符将嵌入式查询与布尔表达式组合在一起。
To use a table subquery, you need to use an SQL operator to combine the embedded query with a Boolean expression.
允许子查询中使用相关名称(correlation name)。
两种查询可以用于update语句的where子句中：标量子查询和表子查询。
Two types of queries can be used in the WHERE clause of an UPDATE statement: a scalar subquery and a table subquery.
IWA还无法处理所有类型的查询，比如关联子查询或使用临时表的查询。
IWA does not handle all types of queries yet, such as correlated sub-queries or queries using temp tables.
最里边的子查询找出所有需要更新的行；用户可能已经给出了一些条件来限制这些行。
The inner-most sub-select identifies all rows that need to be updated; the user might have given some conditions to restrict the rows.
你不能在CREATETABLE语句中包含AS子查询子句定义一个外键约束。
You cannot define a foreign key constraint in a CREATE TABLE statement that contains an AS subquery clause.
以上查询包含一个相关子查询，因为主查询和子查询依靠于同一个表，即employees表。
The query above contains a correlated subquery, since the main query and the subquery are relaying on the same table, the employees table.
应用推荐