SQL Column Selection & Design

Columns in the SELECT LIST.

How to change Column Names in the SELECT statement.

  • You can select all columns in a table with the * character.
  • Choose selected columns specified by a comma in between.
  • SQL lets you add to and manipulate field name in return to make them easier to read.
  • You have to use apostrophe around the new column name only if the name contain one or more space-characters.
    Example:
    MySQL, Oracle, SQL server, PostgreSQL:
    select First_name as "First Name",
           Last_name as "Last Name" from customers
    You could do the same without the AS word as it is optional.
    MySQL, Oracle, SQL server, PostgreSQL:
    select First_name  "First Name",
           Last_name  "Last Name" from customers
    What ever the result should be:
    First Name Last Name
    Ricard Nixon
    Robert Redford
    Judith Bowman
    Sandra Emerson
    Marcy Darnovsky

How to use Character Strings in the Query Results.

  • Use '(single quotes) to specify a string and the keyword as for a header name in "(double quotes). Some RDBMS will misunderstand if you do not use the keyword as in this case.
  • Some DBMS also handles text and/or header surrounded with only '(single quotes) or "(double quotes).
  • If you need a "(double quotes) inside a "(double quotes) surrounded string you need to provide this in front with two double quotes (""). Oracle can not handle this.
  • If you need a '(single quotes) inside a '(single quotes) surrounded string you need to provide this in front with two single quotes ('').
    Example:
    MySQL, Oracle, SQL server, PostgreSQL:
    SELECT 'The Customer''s name is '   AS "Information",
           first_name AS "First Name", last_name AS "Last Name" FROM customers; 
    The result should be:
    Information First Name Last Name
    The Customer's name is Ricard Nixon
    The Customer's name is Robert Redford
    The Customer's name is Judith Bowman
    The Customer's name is Sandra Emerson
    The Customer's name is Marcy Darnovsky
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