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For 2021 - online Python 3 training - see ((here)).

Our plans were to retire in summer 2020 and see the world, but Coronavirus has lead us into a lot of lockdown programming in Python 3 and PHP 7.
We can now offer tailored online training - small groups, real tutors - works really well for groups of 4 to 14 delegates. Anywhere in the world; course language English.

Please ask about private 'maintenance' training for Python 2, Tcl, Perl, PHP, Lua, etc.
SELECT in MySQL - choosing the rows you want

The SELECT command in MySQL allows you to examine rows in a table (or more than one table if you like). Good news - but sometimes there's an awful lot of data and you just want rows chosen by particular criteria, or just the first (so many) rows.

The WHERE clause on your select allows you to write a number of conditions which can be linked with AND and OR keywords, and there's a great deal of choice in the conditions. Here are some examples:

WHERE name = "Graham"
Will look for the string Graham (exactly) and nothing else in the field called name. Note that this selection is case sensitive if name is specified as being a binary field, and case insensitive otherwise.

WHERE name IN ("Graham","Lisa","Leah")
Will look for any one of the strings Graham Lisa or Leah (exactly in each case; same rule about case as in the example above).

WHERE name LIKE "%Graham%"
Will return any row that contains the word Graham within the name field. This is similar to file name matching (also known as globbing) except that the % metacharacter means "anything" and the _ character (that's an underscore) means any one character ... in place of * and ? in file name matching.

WHERE name RLIKE "^[[:graph:]]+$"
Will return any row with a single name in the name field - this is a regular expression which provides a huge flexibility in matching. Regular Expressions are notable in that you can ask a lot in a very obtuse string of just a few characters!
(written 2005-11-22, updated 2006-06-05)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
S157 - More MySQL commands
  [158] MySQL - LEFT JOIN and RIGHT JOIN, INNER JOIN and OUTER JOIN - (2004-12-20)
  [159] MySQL - Optimising Selects - (2004-12-21)
  [279] Getting a list of unique values from a MySQL column - (2005-04-14)
  [449] Matching in MySQL - (2005-09-24)
  [494] MySQL - a score of things to remember - (2005-11-12)
  [513] MySQL - JOIN or WHERE to link tables correctly? - (2005-12-01)
  [515] MySQL - an FAQ - (2005-12-03)
  [517] An occasional chance, and reducing data to manageable levels - (2005-12-04)
  [567] Combining similar rows from a MySQL database select - (2006-01-17)
  [572] Giving the researcher power over database analysis - (2006-01-22)
  [581] Saving a MySQL query results to your local disc for Excel - (2006-01-29)
  [591] Key facts - SQL and MySQL - (2006-02-04)
  [673] Helicopter views and tartans - (2006-04-06)
  [1213] MySQL - the order of clauses and the order of actions - (2007-06-01)
  [1235] Outputting numbers as words - MySQL with Perl or PHP - (2007-06-17)
  [1331] MySQL joins revisited - (2007-09-03)
  [1574] Joining MySQL tables revisited - finding nonmatching records, etc - (2008-03-15)
  [1735] Finding words and work boundaries (MySQL, Perl, PHP) - (2008-08-03)
  [1904] Ruby, Perl, Linux, MySQL - some training notes - (2008-11-23)
  [2110] MySQL - looking for records in one table that do NOT correspond to records in another table - (2009-03-31)
  [2259] Grouping rows for a summary report - MySQL and PHP - (2009-06-27)
  [2448] MySQL - efficiency and other topics - (2009-10-10)
  [2643] Relating tables with joins in MySQL - (2010-02-21)
  [2644] Counting rows in joined MySQL tables - (2010-02-22)
  [2645] Optimising and caching your MySQL enquiries - (2010-02-22)
  [2647] Removing duplicates from a MySQL table - (2010-02-22)
  [3061] Databases - why data is split into separate tables, and how to join them - (2010-11-20)
  [3270] SQL - Data v Metadata, and the various stages of data selection - (2011-04-29)
  [4481] Extracting data from backups to restore selected rows from MySQL tables - (2015-05-01)

S152 - SQL Primer as Used in MySQL
  [270] NULL in MySQL - (2005-04-06)
  [2240] How do I query a database (MySQL)? - (2009-06-15)
  [3060] INSERT, DELETE, REPLACE and UPDATE - changing the content of SQL tables - (2010-11-19)
  [4007] Which database should I use? MySQL v SQLite - (2013-02-16)


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