diff options
Diffstat (limited to 'Docs/manual.texi')
| -rw-r--r-- | Docs/manual.texi | 71 |
1 files changed, 66 insertions, 5 deletions
diff --git a/Docs/manual.texi b/Docs/manual.texi index 344fb942dd1..04cfbdfabd9 100644 --- a/Docs/manual.texi +++ b/Docs/manual.texi @@ -3380,13 +3380,9 @@ of contributing to the MySQL development while getting something useful in return, is to purchase support directly from MySQL AB. @end itemize -For examples of situations when a commercial license is needed, please -visit the online manual at @uref{http://www.mysql.com/doc/}. - For buying commercial licenses and support, please visit the order section at @uref{https://order.mysql.com/}. - @node Using the MySQL server for free under GPL, , Using the MySQL server under a commercial license, MySQL server licenses @subsection Using the MySQL server for free under GPL @@ -14653,6 +14649,7 @@ mysql> SELECT * FROM shop; * example-Foreign keys:: Using foreign keys * Searching on two keys:: Searching on Two Keys * Calculating days:: Calculating visits per day +* example-AUTO_INCREMENT:: Using AUTO_INCREMENT @end menu @@ -14951,7 +14948,7 @@ DROP TABLE tmp; The above way to solve this query is in effect a @code{UNION} of two queries. -@node Calculating days, , Searching on two keys, Examples +@node Calculating days, example-AUTO_INCREMENT, Searching on two keys, Examples @subsection Calculating visits per day @findex BIT_OR @@ -14982,6 +14979,67 @@ The above calculates how many different days was used for a given year/month combination, with automatic removal of duplicate entries. +@node example-AUTO_INCREMENT, , Calculating days, Examples +@subsection Using AUTO_INCREMENT + +@cindex AUTO_INCREMENT +The @code{AUTO_INCREMENT} attribute can be used to generate an unique +identity for new rows: + +@example +CREATE TABLE animals (id mediumint not null auto_increment, +name char(30) not null, +primary key (id)); +INSERT INTO animals (name) values ("dog"),("cat"),("penguin"),("lax"),("whale"); +SELECT * FROM animals; + +Which returns: + ++----+---------+ +| id | name | ++----+---------+ +| 1 | dog | +| 2 | cat | +| 3 | penguin | +| 4 | lax | +| 5 | whale | ++----+---------+ +@end example + +For MyISAM and BDB tables you can specify @code{AUTO_INCREMENT} on +secondary column in a multi-column key. In this case the generated +value for the autoincrement column is calculated as +@code{MAX(auto_increment_column)+1) WHERE prefix=given-prefix}. This is +useful when you want to put data into ordered groups. + +@example +CREATE TABLE animals (grp enum ('fish','mammal','bird') not null, +id mediumint not null auto_increment, +name char(30) not null, +primary key (grp,id)); +INSERT INTO animals (grp,name) values ("mammal","dog"),("mammal","cat"),("bird","penguin"),("fish","lax"),("mammal","whale"); +SELECT * FROM animals order by grp,id; + +Which returns: + ++--------+----+---------+ +| grp | id | name | ++--------+----+---------+ +| fish | 1 | lax | +| mammal | 1 | dog | +| mammal | 2 | cat | +| mammal | 3 | whale | +| bird | 1 | penguin | ++--------+----+---------+ +@end example + +Note that in this case, the auto_increment value will be reused if you +delete the row with the biggest auto_increment value in any group. + +You can get the used @code{AUTO_INCREMENT} key with the +@code{LAST_INSERT_ID()} SQL function or the @code{mysql_insert_id()} API +function. + @node Batch mode, Twin, Examples, Tutorial @section Using @code{mysql} in Batch Mode @@ -35026,6 +35084,9 @@ positive number. This is done to avoid precision problems when numbers 'wrap' over from positive to negative and also to ensure that one doesn't accidentally get an auto_increment column that contains 0. +In MyISAM and BDB tables you can specify @code{AUTO_INCREMENT} secondary +column in a multi-column key. @xref{example-AUTO_INCREMENT}. + @cindex ODBC compatibility @cindex compatibility, with ODBC To make MySQL compatible with some ODBC applications, you can find |