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In-Depth Information
This topic covered a wide array of topics, but they all dealt with how to get information from
a database. Initially, we were introduced to SQL, the language for communicating with a
database. The focus was on using SQL as a query language, while the other aspects of the
language were omitted.
We learned that the key to extracting data with SQL is the SELECT statement, which allows
us to select the columns and tables from which to extract data. We now know how to filter
with the WHERE clause by specifying any number of conditions in order to obtain the res-
ults that suit our particular needs. We were introduced to logical and comparison operators
in order to better manage situational data conditions. We also learned how to manage the
order of results in ascending or descending order based on one or more columns with the
ORDER BY clause.
Using the JOIN statements, we tackled the tricky topic of selecting data from more than one
table. We managed to link two or more tables to form a new results set, and we learned the
importance of the unknown (NULL) value.
We then summarized and aggregated data rather than getting results based on individual re-
cords. Central to this concept, the GROUP BY statement enables us to base the results on
groups of common data. In conjunction with SQL's aggregate functions, such as COUNT,
SUM, AVG, MAX, and MIN, we learned how to manipulate data and calculate specific val-
ues. We also explored the HAVING clause, which filters out the results of groups using vari-
ous conditions. We learned how to add new records to a database using the INSERT INTO
statement, update already existing data with the UPDATE statement, and learned about the
DELETE statement, which allows us to delete all or specific records from a table.
Finally, we learned how to use SQL to define the structure of the database itself. We used
the CREATE DATABASE statement to create a new database from scratch. We also learned
about CREATE/ALTER/DROP TABLE commands to successfully manipulate the structures
of tables.
We at ClydeBank Media would really like to thank you for purchasing our topic. As a
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