Working with Metadata - MySQL - page 363

info = get_enumorset_info ( dbh , db_name , tbl_name , col_name )
puts "Information for #{ db_name } . #{ tbl_name } . #{ col_name } :"
if info . nil?
puts "No information available (not an ENUM or SET column?)"
else
puts "Name: " + info [ "name" ]
puts "Type: " + info [ "type" ]
puts "Legal values: " + info [ "values" ]. join ( "," )
puts "Nullable: " + ( info [ "nullable" ] ? "yes" : "no" )
puts "Default value: " + ( info [ "default" ]. nil? ? "NULL" : info [ "default" ] )
end
That code produces the following output for the item table colors column:

Information for cookbook.item.colors:
Name: colors
Type: enum
Legal values: chartreuse,mauve,lime green,puce
Nullable: yes
Default value: puce
Equivalent routines for other APIs are similar. You can find implementations in the lib
directory of the recipes distribution. Such routines are useful for validation of input
values (see Recipe 12.8 ), and are especially handy for generating list elements in web
forms (see Recipes 20.2 and 20.3 ).

10.8. Getting Server Metadata

Problem
You want the MySQL server to tell you about itself.

Solution
Several SQL functions and SHOW statements return information about the server.

Discussion
MySQL has several SQL functions and statements that provide you with information
about the server itself and about your current client session. The following table shows
a few that you may find useful. Both SHOW statements permit a GLOBAL or SESSION
keyword to select global server values or values specific to your session, and a LIKE
' pattern ' clause for limiting the results to variable names matching the pattern:

Statement Information produced by statement

Server version string

SELECT VERSION()

Default database name ( NULL if none)

SELECT DATABASE()