Educator

SQL Command: SELECT

• The SELECT command is used to retrieve rows from a database whose data match specified criteria. A SELECT command has the following basic syntax:

  SELECT col1Name, col2Name FROM tblName;

• The results of a SELECT query are returned in tabular format with columns ordered by how they are listed in the query.
• To specify the retrieval of all columns from a table, the wildcard character, '*', can be used in place of the list of column names.
  • Note: the columns of the data returned are ordered according to the order of the columns in the table when using the wildcard character.
• WHERE clauses can be used to refine the results of a query. A row will be returned if the expression specified in a WHERE clause, known as a where condition, evaluates TRUE for that row.
• A SELECT query with a WHERE clause has the following syntax:

  SELECT * FROM items WHERE itemID=1001;

• A where condition can contain both logical and comparison operators:
  • Logical: OR, AND, NOT
  • Comparison: =, !=, >, >=, <, <=
• When specifying string literals in where conditions, strings should be enclosed in quotation marks (single or double).
  • Note: be sure to properly escape quotation marks
• An ORDER BY clause can be added to a SELECT query to specify how the rows of data retrieved should be ordered. A SELECT query containing an ORDER BY clause has the following syntax:

  SELECT * FROM items ORDER BY price;

• The default sort order is ascending. Descending order can be specified with the DESC keyword:

  SELECT * FROM items ORDER BY price DESC;

• An ORDER BY clause can specify multiple columns to order the rows by:

  SELECT * FROM items ORDER BY imageFileExt, price;

• Additional Resources:
  • SQL Command Reference - SELECT