Avoid table scans when using DELETE on a table on which no SELECT has been done.

shell> scripts/mysql_install_db

shell> chown -R mysql /usr/local/mysql

shell> chgrp -R mysql /usr/local/mysql

shell> chown -R root /usr/local/mysql/bin/

shell> bin/safe_mysqld --user=mysql &

@end example

A large integer. The signed range is @code{-9223372036854775808} to

@code{9223372036854775807}. The unsigned range is @code{0} to

@code{18446744073709551615}.  Note that all arithmetic is done using

signed @code{BIGINT} or @code{DOUBLE} values, so you shouldn't use

unsigned big integers larger than @code{9223372036854775807} (63 bits)

except with bit functions!  Note that @samp{-}, @samp{+}, and @samp{*}

will use @code{BIGINT} arithmetic when both arguments are @code{INTEGER}

values!  This means that if you multiply two big integers (or results

from functions that return integers) you may get unexpected results if

the result is larger than @code{9223372036854775807}.

@code{18446744073709551615}.

Some things you should be aware about @code{BIGINT} columns:

@itemize @bullet

@item

As all arithmetic is done using signed @code{BIGINT} or @code{DOUBLE}

values, so you shouldn't use unsigned big integers larger than

@code{9223372036854775807} (63 bits) except with bit functions! If you

do that, some of the last digits in the result may be wrong because of

rounding errors when converting the @code{BIGINT} to a @code{DOUBLE}.

@item

You can always store an exact integer value in a @code{BIGINT} column by

storing it as a string, as there is in this case there will be no

intermediate double representation.

@item

@samp{-}, @samp{+}, and @samp{*} will use @code{BIGINT} arithmetic when

both arguments are @code{INTEGER} values!  This means that if you

multiply two big integers (or results from functions that return

integers) you may get unexpected results when the result is larger than

@code{9223372036854775807}.

@end itemize

@cindex floating-point number

@tindex FLOAT

relevant columns is the best way to improve the performance of @code{SELECT}

operations.

A table may have up to 16 indexes.  The maximum index length is

256 bytes, although this may be changed when compiling @strong{MySQL}.

The maximum number of keys and the maximum index length is defined per

table handler. @xref{Table types}. You can with all table handlers have

at least 16 keys and a total index length of at least 256 bytes.

For @code{CHAR} and @code{VARCHAR} columns, you can index a prefix of a

column.  This is much faster and requires less disk space than indexing the

@cindex multi-column indexes

@cindex indexes, multi-column

@cindex keys, multi-column

@node Multiple-column indexes, Other-vendor column types, Indexes, Column types

@subsection Multiple-column Indexes

row.

@item

@tindex PRIMARY KEY

A @code{PRIMARY KEY} is a unique @code{KEY} with the extra constraint

that all key columns must be defined as @code{NOT NULL}.  In @strong{MySQL}

the key is named @code{PRIMARY}. A table can have only one @code{PRIMARY KEY}.

As of @strong{MySQL} Version 3.23.6, you can choose between three basic

table formats (@code{ISAM}, @code{HEAP} and @code{MyISAM}.  Newer

@strong{MySQL} may support additional table type, depending on how you

compile it.

@strong{MySQL} may support additional table type (@code{BDB},

@code{GEMINI} or @code{INNOBASE}), depending on how you compile it.

When you create a new table, you can tell @strong{MySQL} which table

type it should use for the table.  @strong{MySQL} will always create a

@itemize @bullet

@item

If @code{mysqld} is started with @code{--myisam-recover}, @code{MyISAM} tables

will automaticly be repaired on open if the table wasn't closed properly.

There is a flag in the @code{MyISAM} file that indicates whether or not

the table was closed correctly.  If @code{mysqld} is started with

@code{--myisam-recover}, @code{MyISAM} tables will automaticly be

checked and/or repaired on open if the table wasn't closed properly.

@item

You can @code{INSERT} new rows in a table without deleted rows,

while other threads are reading from the table.

@code{NULL} values are allowed in indexed columns.  This takes 0-1

bytes/key.

@item

Maximum key length is now 500 bytes by default. In cases of keys longer

than 250 bytes, a bigger key block size than the default of 1024 bytes

is used for this key.

Maximum key length is 500 bytes by default (can be changed by

recompiling).  In cases of keys longer than 250 bytes, a bigger key

block size than the default of 1024 bytes is used for this key.

@item

Maximum number of keys/table enlarged to 32 as default. This can be

enlarged to 64 without having to recompile @code{myisamchk}.

@item

There is a flag in the @code{MyISAM} file that indicates whether or not the

table was closed correctly.  This will soon be used for automatic repair

in the @strong{MySQL} server.

Maximum number of keys/table is 32 as default. This can be enlarged to 64 

without having to recompile @code{myisamchk}.

@item

@code{myisamchk} will mark tables as checked if one runs it with

@code{--update-state}. @code{myisamchk --fast} will only check those

from the @strong{MySQL} option files. @xref{Option files}.

@example

$dsn = "DBI:mysql:test;mysql_read_default_group=client;"

$dsn = "DBI:mysql:test;mysql_read_default_group=client;mysql_read_default_file=/usr/local/mysql/data/my.cnf"

$dbh = DBI->connect($dsn, $user, $password);

@end example

@itemize @bullet

@item

@code{mysqldump} on a @code{MERGE} table doesn't include the current

mapped tables.

@item

For the moment @code{MATCH} only works with @code{SELECT} statements.

@item

When using @code{SET CHARACTER SET}, one can't use translated

			    limit != HA_POS_ERROR ? TL_WRITE_LOW_PRIORITY :

			    lock_type)))

    DBUG_RETURN(-1);

  table->file->info(HA_STATUS_VARIABLE | HA_STATUS_NO_LOCK);

  thd->proc_info="init";

  if (use_generate_table)

    DBUG_RETURN(generate_table(thd,table_list,table));