subquery

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.

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

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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

To use a table subquery, you need to use an SQL operator to combine the embedded query with a Boolean expression.

Design a query that uses a subquery to select the proper rows for a subscription from a table.

The SUM function is included in a correlated subquery (the SELECT statement in parentheses).

A GROUP BY clause in a subquery that references a column from the outer query returns an error as per the SQL standard.

Each table, view, user-defined function, or subquery appears as a separate window in the Diagram pane.

Using one ORDER BY clause applies only to when using UNION, EXCEPT and INTERSECT in a top-level query and not in a subquery.

The select list of a SELECT statement (either a subquery or an outer query).

In general, explicit casts are often required when the initial subquery returns a literal value or NULL.

To negate a criterion that contains a subquery , you cannot place the NOT operator in the Column cell of the Grid pane .

You may have noticed that the subquery contains a reference to the id column from the customer table.

Subqueries used in the subquery comparison test and set membership test both return data values from the subquery table.

Sometimes, however, you may be more concerned with whether the subquery returns any results, rather than which results.

You can use a scalar subquery to select a specific value that will be used in the expression of the WHERE clause.

The main query asks for ; the subquery specifies properties of child .

Each sggrep command can specify both the main query and a subquery.

These subquery sections will appear in the order that the database server executes the queries.

Rows for which the SUBSCRIBE BY value is in the subquery result set are extracted or synchronized.

Examples of operation merging include view merging and subquery-to-join transformation.

You use a subquery, also called a nested query, to calculate a value for use as a criterion.

You can use any valid SQL keyword in a subquery, excluding data-definition keywords.

In this example, the subquery calculates exactly one value: the average quantity from the sales_order_items table.

The source table or tables become part of a subquery.

It is strongly recommended that all such logic be expressed in a join filter rather than a subquery.

The HAVING clause then checks if each average quantity is more than double the quantity found by the subquery.

The replication tools use the subquery for extraction and synchronization only.

The select list of the subquery must match the column list of the INSERT statement.

The existence test (EXISTS) checks whether a subquery produces any rows of query results.

When a subquery appears in the HAVING clause, like any expression in the HAVING clause, it is used as part of the row group selection.

Casts must always be applied to NULL values in the initial subquery.

The product. Id column in this subquery is an example of an outer reference.

A subquery in a comparison test must return exactly one value.

Specifies a subquery to test for the existence of rows.

In this case, the test returns TRUE if the subquery produces no rows, and FALSE otherwise.

The subquery calculates the average quantity of items in the sales_order_items table.

What fraction of queries that were optimized contained a subquery?

Determines whether a specified value matches any value in a subquery or a list.

When this statement is executed, the subquery is evaluated first.

It returns the error Subquery allowed only one select list item.

Use the INSERT statement to specify values directly or from a subquery.

When Adaptive Server Anywhere processes a subquery, it caches the result.

A subquery SELECT statement if executed independently of the T-SQL statement, in which it is nested, will return a result set.

An example is a function invoked by a subquery in a WHERE clause.

You can use a nested query, also called a subquery, to create a calculated field.

It's important to note that technically, this is not a join, but a subquery.

This lets you reuse the value produced by these functions in the subquery.

The recursive subquery extends the paths.

A subquery can be used anywhere an expression is allowed.

A subquery that references a column in the outer statement.

You can also preface EXISTS with NOT, to indicate that a subquery should not return any rows.

Is a subquery that retrieves rows from the database.

The recursive subquery cannot contain DISTINCT, or a GROUP BY or an ORDER BY clause.

The sample expressions in the following table match rows based on the results returned by a subquery.

In the example, this is represented by the outermost select statement, which uses S1 as a subquery.

You can do so by using an SQL INSERT statement that uses a subquery to get the values to insert.

Create a view that contains this subquery.

Because the value requested for CustomerID does not exist, the subquery returns no value and the variable is set to NULL.

Instead of using subquery, we join two tables directly.

This statement is represented in the example as subquery S1.

The subquery constructing the product names returns the result as a string that is entitized and then added to the XML.

The recursive subquery can not make use of any aggregate function.

Using a SELECT subquery also lets more than one row be inserted at the same time.

The following example returns a result set with NULL specified in the subquery and still evaluates to TRUE by using EXISTS.

A subquery that returns a result set of one column.

Is a subquery that has a result set of one column.

The subquery is correlated; that is, it contains an outer reference.

The result of that subquery then becomes a value in the WHERE clause expression

Statements that include a subquery usually take one of these formats: WHERE expression

A subquery that follows the keyword EXISTS is converted to a join only if it satisfies the following two conditions

The following is an example showing both a subquery SELECT and a join SELECT that return the same result set

Common SQL keywords that you can use with a subquery

Query with Complex Correlated Subquery May Cause Unexpected Results in Aggregate Functions

Correlated Subquery on Partitioned Views with Text Operations May Cause Access Violation

Better error message when using a subquery that contains a reference to non existing property

Nest a query inside another query or in an expression by using a subquery

Consider this query, whose subquery extracts two columns from the sales_order_items table

Use a subquery as a criterion in a Select query

A subquery with a comparison returns a single value

This query contains an example of a subquery comparison test

Coalesce with Subquery May Generate an Access Violation

Expression that uses a subquery to create a calculated field

A subquery nested in the outer SELECT statement has the following components

By using a SELECT subquery to specify the data values for one or more rows, such as