There is an equivalent join expression that can be substituted for all subquery expressions.
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Database · all questionsIntroduction to SQL
Introduction to SQL
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A dynamic view is one whose contents materialize when referenced.
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SQL is a programming language.
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SELECT DISTINCT is used if a user wishes to see duplicate columns in a query.
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Indexes can usually be created for both primary and secondary keys.
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Each index consumes extra storage space and also requires overhead maintenance time whenever indexed data change value.
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The HAVING clause acts like a WHERE clause, but it identifies groups that meet a criterion, rather than rows.
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SQL is a data sublanguage.
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The qualifier DISTINCT must be used in an SQL statement when we want to eliminate duplicate rows.
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DISTINCT and its counterpart, ALL, can be used more than once in a SELECT statement.
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The result of every SQL query is a table.
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COUNT(field_name) tallies only those rows that contain a value; it ignores all null values.
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SUM, AVG, MIN, and MAX can only be used with numeric columns.
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Most companies keep at least two versions of any database they are using.
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The format SELECT-FROM-WHERE is the fundamental framework of SQL SELECT statements.
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Indexes may be created or dropped at any time.
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The SQL statement: SELECT Number1 + Number 2 AS Total FROM NUMBER_TABLE; adds two numbers from each row together and lists the results in a column named Total.
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ORDER BY can be combined with the SELECT statements.
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Data manipulation language (DML) commands are used to define a database, including creating, altering, and dropping tables and establishing constraints.
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Scalar aggregate are multiple values returned from an SQL query that includes an aggregate function.
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