subquery

美 　英

• 網(wǎng)絡(luò)子查詢；活用子查詢；千變?nèi)f化的子查詢

例句

Within the body of a subquery, it is often necessary to refer to the value of a column in the active row of the main query.

在子查詢的正文中，通常需要引用主查詢的活動(dòng)行中的列的值。

A reference to columns or expressions in the main table(s) is called an outer reference and the subquery is said to be correlated.

對(duì)主表中的列或表達(dá)式的引用被稱作外部引用，并且這種子查詢是相關(guān)的。

The EXISTS condition is TRUE if the subquery result contains at least one row, and FALSE if the subquery result does not contain any rows.

如果子查詢結(jié)果至少包含一行，則EXISTS條件為TRUE；如果子查詢結(jié)果一行也不包含，則條件為FALSE。

Multiple references to such columns in a subquery do not cause the functions to be evaluated multiple times.

在子查詢中對(duì)這些列的多次引用不會(huì)使這些函數(shù)被計(jì)算多次。

Number of optimizations for a query that contains at least one subquery.

包含至少一個(gè)子查詢的查詢的優(yōu)化數(shù)。

Two types of queries can be used in the WHERE clause of an UPDATE statement: a scalar subquery and a table subquery.

兩種查詢可以用于UPDATE語(yǔ)句的WHERE子句中：標(biāo)量子查詢和表子查詢。

The result of the scalar subquery first needs to be transferred to the federated server.

首先需要將標(biāo)量子查詢的結(jié)果傳送到聯(lián)邦服務(wù)器。

The IN operator is one of four SQL operators that you can use with a table subquery.

IN操作符是可以用于表子查詢的四個(gè)SQL操作符之一。

If the subquery (which must have one column) returns one row, then the value of that row is compared to the expression.

如果子查詢（必須含有一列）返回一行，則該行的值將與表達(dá)式進(jìn)行比較。

Casts may be required if the columns of the initial subquery do not have the same domains as those of the recursive subquery.

如果初始子查詢的列與遞歸子查詢的列具有不同的域，則可能需要進(jìn)行轉(zhuǎn)換。

Any null values returned by subquery or expression that are compared to test_expression using IN or NOT IN return UNKNOWN.

subquery或expression使用IN或NOTIN與test_expression比較后返回的所有空值都將返回UNKNOWN。

Is a constant, function, any combination of column names, constants, and functions connected by an operator or operators, or a subquery.

常量、函數(shù)以及由一個(gè)或多個(gè)運(yùn)算符連接的列名、常量和函數(shù)的任意組合，或者是子查詢。

A subquery that references one or more columns from its containing SQL statement is called a correlated subquery.

如果一個(gè)子查詢中引用了包含查詢語(yǔ)句的一個(gè)或多個(gè)字段，則該子查詢就稱為相關(guān)性子查詢。

The SHIP3 operator contains the statement that shows the result of the scalar subquery being bound in as a host variable.

SHIP3操作符包含一個(gè)語(yǔ)句，該語(yǔ)句表明標(biāo)量子查詢的結(jié)果放在一個(gè)主機(jī)變量中。

The query above contains a correlated subquery, since the main query and the subquery are relaying on the same table, the employees table.

以上查詢包含一個(gè)相關(guān)子查詢，因?yàn)?/c>主查詢和子查詢依靠于同一個(gè)表，即employees表。

The last section also describes the ALL, EXISTS, and SOME or ANY predicates, which can be used to express conditions on subquery results.

最后一節(jié)還描述了ALL、EXISTS和SOME或ANY謂詞，這些謂詞可用于表達(dá)子查詢結(jié)果上的條件。

The main query does not contain a GROUP BY clause, and is not an aggregate query, or the subquery returns exactly one value.

主查詢不包含GROUPBY子句并且不是匯總查詢，或者子查詢恰好返回一個(gè)值。

The number of times the subquery and its function is executed can vary with different access paths chosen by the optimizer.

子查詢及其函數(shù)執(zhí)行的次數(shù)會(huì)因優(yōu)化器選擇的訪問路徑的不同而異。

The first is the unnesting of the subquery into a join between the employee and sales_order tables.

第一個(gè)優(yōu)化解除了職員與sales_order表之間連接中的子查詢嵌套。

This extension, specifying a join, can be used instead of a subquery in the WHERE clause to identify rows to be removed.

這個(gè)擴(kuò)展指定聯(lián)接，可在WHERE子句中取代子查詢來標(biāo)識(shí)要刪除的行。

The expression can be a constant or a column name, and the list can be a set of constants or, more commonly, a subquery.

該表達(dá)式可以是一個(gè)常量或一個(gè)列名，而列表可以是一組常量，通常為一個(gè)子查詢。

The database server automatically attempts to convert the values returned by the recursive subquery to match those of the initial query.

數(shù)據(jù)庫(kù)服務(wù)器會(huì)自動(dòng)嘗試轉(zhuǎn)換由遞歸子查詢返回的值，以便與初始查詢的那些值匹配。

In this case, error 1242 means that the query execution failed because there was a problem in a subquery.

在這里，錯(cuò)誤1242表示查詢操作失敗，由于子查詢有問題。

The previous subquery in this statement cannot be evaluated independently of the outer query.

該語(yǔ)句中前面的子查詢無(wú)法獨(dú)立于外部查詢進(jìn)行計(jì)算。

Used with a subquery to test for the existence of rows returned by the subquery.

與子查詢一起使用，用于測(cè)試是否存在子查詢返回的行。

The only change we made here was to get rid of the subquery in the original qeury.

這里我們所做的惟一更改就是去掉了原始查詢中的子查詢。

Specifies the name of the table, view, user-defined function, or subquery for the associated data column.

指定表、視圖、用戶定義函數(shù)或關(guān)聯(lián)數(shù)據(jù)列的子查詢的名稱。

EXISTS Use EXISTS in a WHERE clause to indicate that a subquery should return at least one row.

EXISTS在WHERE子句中使用EXISTS可以指示子查詢至少應(yīng)該返回一行。

The SELECT subquery in the INSERT statement can be used to add values into a table from one or more other tables or views.

INSERT語(yǔ)句中的SELECT子查詢可用于將一個(gè)或多個(gè)表或視圖中的值添加到另一個(gè)表中。

Thus, a subquery can be thought of as a temporary table with statement scope.

因此，一個(gè)子查詢可以認(rèn)為是語(yǔ)句范圍內(nèi)的臨時(shí)表（內(nèi)聯(lián)視圖）。

Specifies the conditions for the rows returned in the result set for a SELECT statement, query expression, or subquery.

指定要在SELECT語(yǔ)句、查詢表達(dá)式或子查詢的結(jié)果集中返回的行的條件。

Explicit casts may also be required when the initial subquery selects values from different columns than the recursive subquery.

當(dāng)初始子查詢從與遞歸子查詢不同的列中選擇值時(shí)，也可能需要進(jìn)行顯式轉(zhuǎn)換。

ALL Use ALL in a WHERE clause to retrieve rows that satisfy the condition when compared to every row returned by the subquery.

ALL在WHERE子句中使用ALL，可以檢索在與子查詢返回的每個(gè)行進(jìn)行比較時(shí)滿足條件的行。

A subquery can appear anywhere an expression can be used, if it returns a single value.

任何可以使用表達(dá)式的地方都可以使用子查詢，只要它返回的是單個(gè)值。

The expression in the following table is one example of a calculated field that results from a subquery.

下表中的表達(dá)式便是使用子查詢生成計(jì)算字段的一個(gè)示例。

If your application requires a row filter to use a subsquery, ensure that the subquery only references lookup data that does not change.

如果您的應(yīng)用程序要求行篩選器使用子查詢，請(qǐng)確保子查詢僅引用不發(fā)生更改的查找數(shù)據(jù)。

The expression cannot be a subquery or include an alias data type.

表達(dá)式不能是子查詢，也不能包含別名數(shù)據(jù)類型。

You do not have to try this approach with queries that contain the IN subquery clause.

對(duì)包含IN子查詢子句的查詢，不必使用此方法。

The subscription_list column is used for log scanning and the subquery is used for extraction and synchronization.

subscription_list列用于日志掃描，子查詢用于抽取和同步。

The subquery in this statement is absurdly simple, and completely unnecessary, but it does serve to illustrate a point.

這個(gè)子查詢非常簡(jiǎn)單，并且完全沒有必要，但是它能說明一點(diǎn)。