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This chapter introduced sample syntax and results for
basic kinds of SELECT statements that are
used to query a relational database. The section Single-Table SELECT Statements shows how to perform the following actions:
- Select columns and rows from a table with the Projection and FROM clauses
- Select rows from a table with the Projection, FROM,
and WHERE clauses
- Use the DISTINCT or UNIQUE keyword
in the Projection clause to eliminate duplicate rows from query
results
- Sort retrieved data with the ORDER BY clause
and the DESC keyword
- Select and order data values that contains non-English characters
- Use the BETWEEN, IN, MATCHES,
and LIKE keywords and various relational
operators in the WHERE clause to create
comparison conditions
- Create comparison conditions that include values, exclude values,
find a range of values (with keywords, relational operators, and
subscripting), and find a subset of values
- Use exact-text comparisons, variable-length wildcards, and restricted
and unrestricted wildcards to perform variable text searches
- Use the logical operators AND, OR,
and NOT to connect search conditions or
Boolean expressions in a WHERE clause
- Use the ESCAPE keyword to protect special
characters in a query
- Search for NULL values with the IS NULL and IS NOT NULL keywords
in the WHERE clause
- Use the FIRST clause to specify that
a query returns only a specified number of the rows that match the
conditions of the SELECT statement
- Use arithmetic operators in the Projection clause to perform
computations on number fields and display derived data
- Use substrings and subscripting to tailor your queries
- Assign display labels to computed columns as a formatting tool
for reports
This chapter also introduced simple join conditions that enable
you to select and display data from two or more tables. The section Multiple-Table SELECT Statements describes how to perform the following
actions:
- Create a Cartesian product
- Create a CROSS JOIN, which creates a Cartesian product
- Include a WHERE clause with a valid
join condition in your query to constrain a Cartesian product
- Define and create a natural join and an equi-join
- Join two or more tables on one or more columns
- Use aliases as a shortcut in multiple-table queries
- Retrieve selected data into a separate, temporary table with
the INTO TEMP clause
to perform computations outside the database
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