erge with 4.0 + updates for column types

* HP-UX 10.20::                 HP-UX 10.20 notes

* HP-UX 11.x::                  HP-UX 11.x notes

* Mac OS X::                    Mac OS X notes

* BEOS::                        

* BEOS::                        BeOS Notes

Linux Notes (All Linux Versions)

* Linux-Alpha::                 Linux-Alpha notes

* MKLinux::                     MkLinux notes

* Qube2::                       Qube2 Linux notes

* Linux-Ia64::                  

* Linux-Ia64::                  Linux-Ia64 notes

BSD/OS Notes

* example-Maximum-row::         The row holding the maximum of a certain column

* example-Maximum-column-group::  Maximum of column per group

* example-Maximum-column-group-row::  The rows holding the group-wise maximum of a certain field

* example-user-variables::      

* example-user-variables::      Using user variables

* example-Foreign keys::        Using foreign keys

Creating and Using a Database

* Estimating performance::      Estimating query performance

* SELECT speed::                Speed of @code{SELECT} queries

* Where optimizations::         How MySQL optimizes @code{WHERE} clauses

* DISTINCT optimization::       

* DISTINCT optimization::       How MySQL Optimizes @code{DISTINCT}

* LEFT JOIN optimization::      How MySQL optimizes @code{LEFT JOIN}

* LIMIT optimization::          How MySQL optimizes @code{LIMIT}

* Insert speed::                Speed of @code{INSERT} queries

MySQL Utilites

* Programs::                    What do the executables do?

* safe_mysqld::                 

* safe_mysqld::                 safe_mysqld, the wrapper around mysqld

* mysqld_multi::                Program for managing multiple @strong{MySQL} servers

* mysql::                       The command line tool

* mysqladmin::                  Administering a @strong{MySQL} server

* Packet too large::            @code{Packet too large} error

* Communication errors::        Communication errors / Aborted connection

* Full table::                  @code{The table is full} error

* Cannot create::               

* Cannot create::               @code{Can't create/write to file} Error

* Commands out of sync::        @code{Commands out of sync} error in client

* Ignoring user::               @code{Ignoring user} error

* Cannot find table::           @code{Table 'xxx' doesn't exist} error

* Log Replication::             Database replication with  update log

* Backup::                      Database backups

* Update log::                  The update log

* Binary log::                  

* Binary log::                  The binary log

* Slow query log::              Log of slow queries

* Multiple servers::            Running multiple @strong{MySQL} servers on the same machine

MySQL change history

* News-4.0.x::                  Changes in release 4.0 (development release)

* News-3.23.x::                 Changes in release 3.23.x (Recommended; Gamma)

* News-3.22.x::                 Changes in release 3.22.x (Still supported)

* News-3.21.x::                 Changes in release 3.21.x

* News-3.20.x::                 Changes in release 3.20.x

* News-3.19.x::                 Changes in release 3.19.x

Changes in release 4.0 (Alpha)

* News-4.0.0::                  Changes in release 4.0.0

Changes in release 3.23.x  (Recommended; Gamma)

* News-3.23.30::                

* News-3.23.30::                Changes in release 3.23.30

* News-3.23.29::                Changes in release 3.23.29

* News-3.23.28::                Changes in release 3.23.28

* News-3.23.27::                Changes in release 3.23.27

* Debugging server::            Debugging a @strong{MySQL} server

* Debugging client::            Debugging a @strong{MySQL} client

* The DBUG package::            The DBUG package

* Locking methods::             

* Locking methods::             Locking methods

* RTS-threads::                 Comments about RTS threads

* Thread packages::             Differences between different thread packages

* HP-UX 10.20::                 HP-UX 10.20 notes

* HP-UX 11.x::                  HP-UX 11.x notes

* Mac OS X::                    Mac OS X notes

* BEOS::                        

* BEOS::                        BeOS Notes

@end menu

* Linux-Alpha::                 Linux-Alpha notes

* MKLinux::                     MkLinux notes

* Qube2::                       Qube2 Linux notes

* Linux-Ia64::                  

* Linux-Ia64::                  Linux-Ia64 notes

@end menu

@node Linux-x86, Linux-RedHat50, Linux, Linux

In @strong{MySQL} Version 3.23, this is a true floating-point value.  In

earlier @strong{MySQL} versions, @code{FLOAT(precision)} always has 2 decimals.

Note that using @code{FLOAT} may give you some unexpected problems as

all calculation in @code{MySQL} is done with double precision.

@xref{No matching rows}.

@cindex ODBC compatibility

@cindex compatibility, with ODBC

This syntax is provided for ODBC compatibility.

An unpacked floating-point number.  Cannot be unsigned.  Behaves like a

@code{CHAR} column: ``unpacked'' means the number is stored as a string,

using one character for each digit of the value.  The decimal point

and, for negative numbers, the @samp{-} sign, are not counted in M.  If

@code{D} is 0, values will have no decimal point or fractional part.

The maximum range of @code{DECIMAL} values is the same as for

@code{DOUBLE}, but the actual range for a given @code{DECIMAL} column

may be constrained by the choice of @code{M} and @code{D}.

using one character for each digit of the value.  The decimal point and,

for negative numbers, the @samp{-} sign, are not counted in M (but space

for these are reserved). If @code{D} is 0, values will have no decimal

point or fractional part.  The maximum range of @code{DECIMAL} values is

the same as for @code{DOUBLE}, but the actual range for a given

@code{DECIMAL} column may be constrained by the choice of @code{M} and

@code{D}.

If @code{D} is left out it's set to 0. If @code{M} is left out it's set to 10.

Note that in @strong{MySQL} Version 3.22 the @code{M} argument includes the

sign and the decimal point.

Note that in @strong{MySQL} Version 3.22 the @code{M} argument had to

includes the space needed for the sign and the decimal point.

@tindex NUMERIC

@item NUMERIC(M,D) [ZEROFILL]

A date.  The supported range is @code{'1000-01-01'} to @code{'9999-12-31'}.

@strong{MySQL} displays @code{DATE} values in @code{'YYYY-MM-DD'} format, but

allows you to assign values to @code{DATE} columns using either strings or

numbers.

numbers. @xref{DATETIME}.

@tindex DATETIME

@item DATETIME

00:00:00'} to @code{'9999-12-31 23:59:59'}.  @strong{MySQL} displays

@code{DATETIME} values in @code{'YYYY-MM-DD HH:MM:SS'} format, but allows you

to assign values to @code{DATETIME} columns using either strings or numbers.

@xref{DATETIME}.

@tindex TIMESTAMP

@item TIMESTAMP[(M)]

be numbers while other @code{TIMESTAMP(X)} columns are reported to be

strings.  This is just to ensure that one can reliably dump and restore

the table with these types!

@xref{DATETIME}.

@tindex TIME

@item TIME

A time.  The range is @code{'-838:59:59'} to @code{'838:59:59'}.

@strong{MySQL} displays @code{TIME} values in @code{'HH:MM:SS'} format, but

allows you to assign values to @code{TIME} columns using either strings or

numbers.

numbers. @xref{TIME}.

@tindex YEAR

@item YEAR[(2|4)]

and 1970-2069 if you use the 2-digit format (70-69).  @strong{MySQL} displays

@code{YEAR} values in @code{YYYY} format, but allows you to assign values to

@code{YEAR} columns using either strings or numbers. (The @code{YEAR} type is

new in @strong{MySQL} Version 3.22.)

new in @strong{MySQL} Version 3.22.). @xref{YEAR}.

@tindex NATIONAL CHAR

@tindex NCHAR

actually use the value.  This is also quite nice when you need a

column that only can take 2 values: A @code{CHAR(0)}, that is not defined

as @code{NOT NULL}, will only occupy one bit and can only take 2 values:

@code{NULL} or @code{""}.

@code{NULL} or @code{""}. @xref{CHAR}.

@tindex CHARACTER VARYING

@tindex CHAR VARYING

given. @xref{Silent column changes}.

@code{VARCHAR} is a shorthand for @code{CHARACTER VARYING}.

@xref{CHAR}.

@tindex TINYBLOB

@tindex TINYTEXT

@itemx TINYTEXT

A @code{BLOB} or @code{TEXT} column with a maximum length of 255 (2^8 - 1)

characters. @xref{Silent column changes}.

characters. @xref{Silent column changes}. @xref{BLOB}.

@tindex BLOB

@tindex TEXT

@itemx TEXT

A @code{BLOB} or @code{TEXT} column with a maximum length of 65535 (2^16 - 1)

characters. @xref{Silent column changes}.

characters. @xref{Silent column changes}. @xref{BLOB}.

@tindex MEDIUMBLOB

@tindex MEDIUMTEXT

@itemx MEDIUMTEXT

A @code{BLOB} or @code{TEXT} column with a maximum length of 16777215

(2^24 - 1) characters. @xref{Silent column changes}.

(2^24 - 1) characters. @xref{Silent column changes}. @xref{BLOB}.

@tindex LONGBLOB

@tindex LONGTEXT

(2^32 - 1) characters. @xref{Silent column changes}.  Note that because

the server/client protocol and MyISAM tables has currently a limit of

16M per communication packet / table row, you can't yet use this

the whole range of this type.

the whole range of this type. @xref{BLOB}.

@tindex ENUM

@item ENUM('value1','value2',...)

An enumeration.

A string object that can have only one value, chosen from the list of values

@code{'value1'}, @code{'value2'}, @code{...}, or @code{NULL}.  An @code{ENUM}

can have a maximum of 65535 distinct values.

An enumeration.  A string object that can have only one value, chosen

from the list of values @code{'value1'}, @code{'value2'}, @code{...},

@code{NULL} or the special @code{""} error value.  An @code{ENUM} can

have a maximum of 65535 distinct values. @xref{ENUM}.

@tindex SET

@item SET('value1','value2',...)

A set.  A string object that can have zero or more values, each of which must

be chosen from the list of values @code{'value1'}, @code{'value2'},

@code{...} A @code{SET} can have a maximum of 64 members.

@code{...} A @code{SET} can have a maximum of 64 members. @xref{SET}.

@end table

@menu

@cindex numeric types

@cindex types, numeric

@subheading Numeric types

@subheading Storage requirements for numeric types

@multitable @columnfractions .5 .5

@item @strong{Column type} @tab @strong{Storage required}

@item @code{DOUBLE}        @tab 8 bytes

@item @code{DOUBLE PRECISION} @tab 8 bytes

@item @code{REAL}         @tab 8 bytes

@item @code{DECIMAL(M,D)} @tab @code{M} bytes (@code{D}+2, if @code{M < D})

@item @code{NUMERIC(M,D)} @tab @code{M} bytes (@code{D}+2, if @code{M < D})

@item @code{DECIMAL(M,D)} @tab @code{M+2} bytes if D > 0, @code{M+1} bytes if D = 0 (@code{D}+2, if @code{M < D})

@item @code{NUMERIC(M,D)} @tab @code{M+2} bytes if D > 0, @code{M+1} bytes if D = 0 (@code{D}+2, if @code{M < D})

@end multitable

@cindex date types

@cindex time types

@cindex types, date

@cindex types, time

@subheading Date and time types

@subheading Storage requirements for date and time types

@multitable @columnfractions .5 .5

@item @strong{Column type} @tab @strong{Storage required}

@item @code{YEAR}          @tab 1 byte

@end multitable

@subheading String types

@subheading Storage requirements for string types

@multitable @columnfractions .5 .5

@item @strong{Column type} @tab @strong{Storage required}

on the number of set members (64 members maximum)

@end multitable

@cindex BLOB, size

@cindex TEXT, size

@cindex VARCHAR, size

@code{VARCHAR} and the @code{BLOB} and @code{TEXT} types are variable-length

types, for which the storage requirements depend on the actual length of

column values (represented by @code{L} in the preceding table), rather than

The @code{BLOB} and @code{TEXT} types require 1, 2, 3, or 4 bytes to record

the length of the column value, depending on the maximum possible length of

the type.

the type.  @xref{BLOB}.

If a table includes any variable-length column types, the record format will

also be variable-length.  Note that when a table is created, @strong{MySQL}

may, under certain conditions, change a column from a variable-length type to a

fixed-length type, or vice-versa.  @xref{Silent column changes}.

The size of an @code{ENUM} object is determined by the number of different

enumeration values.  One byte is used for enumerations with up to 255 possible

values.  Two bytes are used for enumerations with up to 65535 values.

@cindex ENUM, size

The size of an @code{ENUM} object is determined by the number of

different enumeration values.  One byte is used for enumerations with up

to 255 possible values.  Two bytes are used for enumerations with up to

65535 values. @xref{ENUM}.

@cindex SET, size

The size of a @code{SET} object is determined by the number of different

set members.  If the set size is @code{N}, the object occupies @code{(N+7)/8}

bytes, rounded up to 1, 2, 3, 4, or 8 bytes.  A @code{SET} can have a maximum

of 64 members.

of 64 members. @xref{SET}.

@node Numeric types, Date and time types, Storage requirements, Column types

@subsection Numeric Types

@example

DELETE [LOW_PRIORITY] FROM tbl_name

    [WHERE where_definition] [LIMIT rows]

    [WHERE where_definition]

@c    [ORDER BY ...]

    [LIMIT rows]

@end example

@code{DELETE} deletes rows from @code{tbl_name} that satisfy the condition

given by @code{where_definition}, and returns the number of records deleted.

@c If an @code{ORDER BY} clause is used, the rows will be deleted in that order.

@c This is really only useful in conjunction with @code{LIMIT}.  For example:

@c @example

@c DELETE FROM somelog

@c WHERE user = 'jcole'

@c ORDER BY timestamp

@c LIMIT 1

@c @end example

@c This will delete the oldest entry (by @code{timestamp}) where the row matches

@c the @code{WHERE} clause.

If you issue a @code{DELETE} with no @code{WHERE} clause, all rows are

deleted.  If you do this in @code{AUTOCOMMIT} mode, this works as

@code{TRUNCATE}. @xref{TRUNCATE}. One problem with this is that

@section @code{UPDATE} Syntax

@example

UPDATE [LOW_PRIORITY] [IGNORE] tbl_name SET col_name1=expr1,col_name2=expr2,...

    [WHERE where_definition] [LIMIT #]

UPDATE [LOW_PRIORITY] [IGNORE] tbl_name

    SET col_name1=expr1, [col_name2=expr2, ...]

    [WHERE where_definition]

    [ORDER BY ...]

    [LIMIT #]

@end example

@code{UPDATE} updates columns in existing table rows with new values.  The

@code{SET} clause indicates which columns to modify and the values they

should be given.  The @code{WHERE} clause, if given, specifies which rows

should be updated.  Otherwise all rows are updated.

@code{UPDATE} updates columns in existing table rows with new values.

The @code{SET} clause indicates which columns to modify and the values

they should be given.  The @code{WHERE} clause, if given, specifies

which rows should be updated.  Otherwise all rows are updated. If the

@code{ORDER BY} clause is specified, the rows will be updated in the

order that is specified.

If you specify the keyword @code{LOW_PRIORITY}, execution of the

@code{UPDATE} is delayed until no other clients are reading from the table.

subsystem)

@end itemize

@cindex threads, display

@cindex processes, display

@findex threads

* example-Maximum-row::         The row holding the maximum of a certain column

* example-Maximum-column-group::  Maximum of column per group

* example-Maximum-column-group-row::  The rows holding the group-wise maximum of a certain field

* example-user-variables::      

* example-user-variables::      Using user variables

* example-Foreign keys::        Using foreign keys

@end menu

@node Getting information, Batch mode, Database use, Tutorial

@section Getting Information About Databases and Tables

What if you forget the name of a database or table, or what the structure of

a given table is (for example, what its columns are called)?  @strong{MySQL}

addresses this problem through several statements that provide information

* Estimating performance::      Estimating query performance

* SELECT speed::                Speed of @code{SELECT} queries

* Where optimizations::         How MySQL optimizes @code{WHERE} clauses

* DISTINCT optimization::       

* DISTINCT optimization::       How MySQL Optimizes @code{DISTINCT}

* LEFT JOIN optimization::      How MySQL optimizes @code{LEFT JOIN}

* LIMIT optimization::          How MySQL optimizes @code{LIMIT}

* Insert speed::                Speed of @code{INSERT} queries

@menu

* Programs::                    What do the executables do?

* safe_mysqld::                 

* safe_mysqld::                 safe_mysqld, the wrapper around mysqld

* mysqld_multi::                Program for managing multiple @strong{MySQL} servers

* mysql::                       The command line tool

* mysqladmin::                  Administering a @strong{MySQL} server

* Packet too large::            @code{Packet too large} error

* Communication errors::        Communication errors / Aborted connection

* Full table::                  @code{The table is full} error

* Cannot create::               

* Cannot create::               @code{Can't create/write to file} Error

* Commands out of sync::        @code{Commands out of sync} error in client

* Ignoring user::               @code{Ignoring user} error

* Cannot find table::           @code{Table 'xxx' doesn't exist} error

* Log Replication::             Database replication with  update log

* Backup::                      Database backups

* Update log::                  The update log

* Binary log::                  

* Binary log::                  The binary log

* Slow query log::              Log of slow queries

* Multiple servers::            Running multiple @strong{MySQL} servers on the same machine

@end menu

and searching. Full-text index in @strong{MySQL} is an

index of type @code{FULLTEXT}. @code{FULLTEXT} indexes can be created from

@code{VARCHAR} and @code{TEXT} columns at @code{CREATE TABLE} time or added

later with @code{ALTER TABLE} or @code{CREATE INDEX}. Full-text search is

performed with the @code{MATCH} function:

later with @code{ALTER TABLE} or @code{CREATE INDEX}. For big datasets,

adding @code{FULLTEXT} index with @code{ALTER TABLE}

(or @code{CREATE INDEX}) would be much faster, than inserting rows into

the empty table with @code{FULLTEXT} index.

Full-text search is

performed with the @code{MATCH} function.

@example

mysql> CREATE TABLE t (a VARCHAR(200), b TEXT, FULLTEXT (a,b));

this means that the version has not yet been released!

@menu

* News-4.0.x::                  Changes in release 4.0 (development version)

* News-3.23.x::                 Changes in release 3.23.x (Recommended; Gamma)

* News-3.22.x::                 Changes in release 3.22.x (Still supported)

* News-3.21.x::                 Changes in release 3.21.x

* News-3.19.x::                 Changes in release 3.19.x

@end menu

@node News-3.23.x, News-3.22.x, News, News

@node News-4.0.x, News-3.23.x, News, News

@appendixsec Changes in release 4.0 (Alpha)

We have now started to work on MySQL 4.0.  We will update this section

as we add new features so that other can follow our development.

Our TODO section contains what we plan to have in 4.0. @xref{TODO MySQL 4.0}.

@menu

* News-4.0.0::                  Changes in release 4.0

@end menu

@node News-4.0.0,  , News-4.0.x, News-4.0.x

@appendixsubsec Changes in release 4.0

@itemize @bullet

@item

Added @code{ORDER BY} to @code{DELETE}.

@end itemize

@node News-3.23.x, News-3.22.x, News-4.0.x, News

@appendixsec Changes in release 3.23.x  (Recommended; Gamma)

The 3.23 release has several major new features that are not

a month to make after which we want to stabilize it and start working on

Version 4.1.  Version 4.0 should have the following new features:

The news section for 4.0 includes a list of the features we have already

implemented in the 4.0 tree. @xref{News-4.0.x}.

@itemize @bullet

@item

New table definition file format (@code{.frm} files) This will enable us

one can use it in a threaded client to run different queries in each

thread.

@item

@code{SHOW DATABASE} should only show the database which you have some kind

of access privilege to.

@item

Online backup with very low performance penalty.  The online backup will

make it easy to add a new replication slave without taking down the

master.

* Debugging server::            Debugging a @strong{MySQL} server

* Debugging client::            Debugging a @strong{MySQL} client

* The DBUG package::            The DBUG package

* Locking methods::             

* Locking methods::             Locking methods

* RTS-threads::                 Comments about RTS threads

* Thread packages::             Differences between different thread packages

@end menu