CODEWITHSUNDEEP
mysqldatabase
Ibrahim Azhar Armar
Ibrahim Azhar Armar

Reputation: 25745

Need Help understanding this piece of MySQL Code

CREATE TABLE `users` (
`ID` int(10) unsigned zerofill NOT NULL auto_increment,
`username` varchar(20) NOT NULL,
PRIMARY KEY  (`ID`),
KEY `Username` (`username`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

what is a) unsigned, zerofill in ID table? b) what do you mean by KEY Username (username) ?

thank you

Upvotes: 0

Views: 110

Answers (4)

sirprize
sirprize

Reputation: 426

Zerofill is used to pad a number with zeros instead of spaces. In this case, the number 1337 would be padded with 6 zeros and shown as 0000001337 because of int(10). Specifying unsigned is not needed since zerofill automatically chooses unsigned, see http://dev.mysql.com/doc/refman/5.0/en/numeric-types.html

KEY foo (bar) creates an index on the bar column. The name of the index is foo.

Upvotes: 0

trickwallett
trickwallett

Reputation: 2468

unsigned = a none positive / negative number, so you couldnt have -1 as the "-" is a sign.

zerofill = fill it with zeros by default. Not necessary as the column's already got the auto_increment / pk attributes

key = index this column i.e. make SELECTS that search on this column faster.

Ta

Upvotes: 2

SeeSoft
SeeSoft

Reputation: 91

here is a partial answer.

a) unsigned means that the value is positive.

b) zerofill means that it will have leftpadding with '0'

ex : without zerofill you have 55 and with you will have 00000055

Regards.

Upvotes: 0

ajreal
ajreal

Reputation: 47321

zerofill - left pad with 0

For example, for a column declared as INT(4) ZEROFILL, a value of 5 is retrieved as 0005.

unsigned is number not less than zero

If you specify ZEROFILL for a numeric column, MySQL automatically adds the UNSIGNED attribute to the column.

Unsigned type can be used to permit only nonnegative numbers in a column or when you need a larger upper numeric range for the column

details : http://dev.mysql.com/doc/refman/5.0/en/numeric-types.html

KEY Username (username) ?

is an index name after Username on column username

details : http://dev.mysql.com/doc/refman/5.0/en/create-table.html

Upvotes: 3

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