Examples - Teradata Database

SQL Data Manipulation Language

Product
Teradata Database
Release Number
16.10
Published
June 2017
Language
English (United States)
Last Update
2018-04-25
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B035-1146
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previous
Product Category
Teradata® Database

Example: Combining Equality and Inequality Conditions in a Correlated Subquery

You can use correlated subqueries to specify a combination of equality and inequality constraints with the subquery.

For example, to select the names of all students who are younger than all students at the same grade, you can perform the following query:

     SELECT name
     FROM student st1
     WHERE age < ALL (SELECT age
                      FROM student st2
                      WHERE st1.grade = st2.grade
                      AND st1.stno <> st2.stno);

Example: Using SELECT COUNT(*) in a Correlated Subquery

Select the names of the publishers whose book count values in the library match the actual count of books.

     SELECT pubname, bookcount
     FROM library
     WHERE (bookcount, pubnum) IN (SELECT COUNT(*), book.pubnum
                                   FROM book
                                   GROUP BY pubnum);

If the book count for a publisher in the library is zero, then the name of that publisher is not returned because no row is returned by the subquery for this publisher.

Note that the result data type for a COUNT operation is different for ANSI and Teradata session modes, as described by the following table. See SQL Functions, Operators, Expressions, and Predicates for details.

IN this session mode … THE data type of the result for a COUNT operation is …
ANSI DECIMAL(p,0)

where p represents the precision of the number.

  • If the DBS Control field MaxDecimal is set to any of the following values, then the value of p is 15.

      0

    15

    18

  • If the DBS Control field MaxDecimal is set to 31, then the value of p is also 31.
  • If the DBS Control field MaxDecimal is set to 38, then the value of p is also 38.
Teradata INTEGER

Another equivalent SELECT statement uses two noncorrelated subqueries to return the same answer set as follows:

     SELECT pub_name, book_count
     FROM library
     WHERE (book_count, pub_num) IN (SELECT COUNT(*), pub_num
                                     FROM book
                                     GROUP BY pub_num)
                          OR NOT IN (SELECT book.pub_num
                                     FROM book
                                     GROUP BY pub_num)
                                 AND book_count = 0;

The following SELECT statement, which is less complicated and more elegant, uses a correlated subquery to return the same correct answer as the previous query.

     SELECT pub_name, book_count
     FROM library
     WHERE book_count IN (SELECT count(*)
                          FROM book
                          WHERE book.pub_num = library.pub_num);