manual.texi Mods to data type sections.

@item

Users of MySQL C API:

@itemize @bullet

@item Check out the @code{mysql_escape_string()} API call.

@item Check out the @code{mysql_real_escape_string()} API call.

@end itemize

@item

Users of MySQL++:

@findex (Control-Z) \z

@item \z

ASCII(26) (Control-Z).  This character can be encoded to allow you to

go around the problem that ASCII(26) stands for END-OF-FILE on Windows.

work around the problem that ASCII(26) stands for END-OF-FILE on Windows.

(ASCII(26) will cause problems if you try to use

@code{mysql database < filename}.)

@cindex quoting binary data

If you want to insert binary data into a @code{BLOB} column, the following

characters must be represented by escape sequences:

If you want to insert binary data into a string column (such as a

@code{BLOB}), the following characters must be represented by escape

sequences:

@table @code

@item NUL

ASCII 0. You should represent this by @samp{\0} (a backslash and an ASCII @samp{0} character).

@cindex quoting

@cindex @code{BLOB}, inserting binary data

@findex mysql_escape_string()

@findex mysql_real_escape_string()

@findex DBI->quote

If you write C code, you can use the C API function

@code{mysql_escape_string()} to escape characters for the @code{INSERT}

@code{mysql_real_escape_string()} to escape characters for the @code{INSERT}

statement.  @xref{C API function overview}.  In Perl, you can use the

@code{quote} method of the @code{DBI} package to convert special

characters to the proper escape sequences.  @xref{Perl DBI Class, , Perl

You should use an escape function on any string that might contain any of the

special characters listed above!

Alternatively, many MySQL APIs provide some sort of placeholder capability

that allows you to insert special markers into a query string, and then bind

data values to them when you issue the query.  In this case, the API takes

case of escaping special characters in the values for you automatically.

@node Number syntax, Hexadecimal values, String syntax, Literals

@subsubsection Numbers

@tindex hexadecimal values

MySQL supports hexadecimal values.  In number context these act

MySQL supports hexadecimal values.  In numeric context these act

like an integer (64-bit precision). In string context these act like a binary

string where each pair of hex digits is converted to a character:

         -> Paul

@end example

The x'hexstring' syntax (new in 4.0) is based on ANSI SQL and the 0x

syntax is based on ODBC.

Hexadecimal strings are often used by ODBC to give values for BLOB columns.

The @code{x'hexstring'} syntax (new in 4.0) is based on ANSI SQL and the

@code{0x} syntax is based on ODBC.  Hexadecimal strings are often used by

ODBC to supply values for @code{BLOB} columns.

You can convert a string or a number to hexadecimal with the @code{HEX()}

function.

you must always quote it with @code{`} when you use it:

@example

SELECT * from `select` where `select`.id > 100;

mysql> SELECT * from `select` where `select`.id > 100;

@end example

In previous versions of MySQL, the name rules are as follows:

@item

A name may start with any character that is legal in a name.  In particular,

a name may start with a number (this differs from many other database

systems!).  However, a name cannot consist @emph{only} of numbers.

a name may start with a digit (this differs from many other database

systems!).  However, a name cannot consist @emph{only} of digits.

@item

You cannot use the @samp{.} character in names because it is used to extend the

In MySQL, databases and tables correspond to directories and files

within those directories.  Consequently, the case sensitivity of the

underlying operating system determines the case sensitivity of database and

table names.  This means database and table names are case sensitive in Unix

and case insensitive in Windows. @xref{Extensions to ANSI}.

table names.  This means database and table names are case insensitive in

Windows, and case sensitive in most varieties of Unix (Mac OS X being an

exception).

@xref{Extensions to ANSI}.

@strong{NOTE:} Although database and table names are case insensitive for

Windows, you should not refer to a given database or table using different

mysql> SELECT * FROM my_table WHERE MY_TABLE.col=1;

@end example

Column names are case insensitive in all cases.

Column names and column aliases are case insensitive in all cases.

Aliases on tables are case sensitive.  The following query would not work

because it refers to the alias both as @code{a} and as @code{A}:

    ->                 WHERE a.col_name = 1 OR A.col_name = 2;

@end example

Aliases on columns are case insensitive.

If you have a problem remembering the used cases for a table names,

If you have trouble remembering the lettercase for database and table names,

adopt a consistent convention, such as always creating databases and

tables using lowercase names.

[,@@variable= ...].

@end example

You can also set a variable in an expression with the @code{@@variable:=expr}

syntax:

You can also assign a value to a variable in statements other than @code{SET}.

However, in this case the assignment operator is @code{:=} rather than

@code{=}, because @code{=} is reserved for comparisons in non-@code{SET}

statements:

@example

select @@t1:=(@@t2:=1)+@@t3:=4,@@t1,@@t2,@@t3;

+----------------------+------+------+------+

@end example

(We had to use the @code{:=} syntax here, because @code{=} was reserved for

comparisons.)

User variables may be used where expressions are allowed.  Note that

this does not currently include use in contexts where a number is explicitly

this does not currently include contexts where a number is explicitly

required, such as in the @code{LIMIT} clause of a @code{SELECT} statement,

or the @code{IGNORE number LINES} clause of a @code{LOAD DATA} statement.

@strong{NOTE:}  In a @code{SELECT} statement, each expression is only

evaluated when it's sent to the client.  This means that in the @code{HAVING},

@strong{NOTE:}  In a @code{SELECT} statement, each expression is evaluated

only when it's sent to the client.  This means that in the @code{HAVING},

@code{GROUP BY}, or @code{ORDER BY} clause, you can't refer to an expression

that involves variables that are set in the @code{SELECT} part. For example,

the following statement will NOT work as expected:

1;

@end example

Note that the @code{--} comment style requires you to have at least one space

after the @code{--}!

Note that the @code{--} (double-dash) comment style requires you to have at

least one space after the second dash!

Although the server understands the comment syntax just described,

there are some limitations on the way that the @code{mysql} client

and when you put commands in a file and tell @code{mysql} to read its

input from that file with @code{mysql < some-file}.

MySQL only supports the @samp{--} ANSI SQL comment style if it is

followed by a space. @xref{ANSI diff comments}.

MySQL supports the @samp{--} ANSI SQL comment style only if the second dash

is followed by a space. @xref{ANSI diff comments}.

@node Reserved words,  , Comments, Language Structure

use the names of datatypes or functions built into MySQL, such as

@code{TIMESTAMP} or @code{GROUP}.  You're allowed to do it (for example,

@code{ABS} is an allowed column name), but whitespace is not allowed between

a function name and the @samp{(} when using functions whose names are also

column names.

a function name and the immediately following @samp{(} when using functions

whose names are also column names.

The following words are explicitly reserved in MySQL. Most of

them are forbidden by ANSI SQL92 as column and/or table names

(for example, @code{group}).

(for example, @code{GROUP}).

A few are reserved because MySQL needs them and is

(currently) using a @code{yacc} parser:

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

@code{18446744073709551615}.

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

Some things you should be aware of with respect to @code{BIGINT} columns:

@itemize @bullet

@item

@cindex rounding errors

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

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

@item

In @code{MIN(big_int_column)} and @code{MAX(big_int_column)}.

@item

When using operators (@code{+}, @code{-}, @code{*} etc) where

When using operators (@code{+}, @code{-}, @code{*}, etc.) where

both operands are integers.

@end itemize

@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.

storing it as a string.  In this case, MySQL will perform a string-to-number

conversion that involves 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

both arguments are 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}.

A small (single-precision) floating-point number. Cannot be unsigned.

Allowable values are @code{@w{-3.402823466E+38}} to

@code{@w{-1.175494351E-38}}, @code{0}, and @code{@w{1.175494351E-38}} to

@code{3.402823466E+38}.  The M is the display width and D is the

@code{3.402823466E+38}.  The @code{M} is the display width and @code{D} is the

number of decimals.  @code{FLOAT} without an argument or with an argument of

<= 24 stands for a single-precision floating-point number.

A normal-size (double-precision) floating-point number. Cannot be

unsigned. Allowable values are @code{@w{-1.7976931348623157E+308}} to

@code{@w{-2.2250738585072014E-308}}, @code{0}, and

@code{2.2250738585072014E-308} to @code{1.7976931348623157E+308}.  The M

is the display width and D is the number of decimals.  @code{DOUBLE}

without an argument or @code{FLOAT(X)} where 25 <= X <= 53 stands for a

double-precision floating-point number.

@code{2.2250738585072014E-308} to @code{1.7976931348623157E+308}.  The

@code{M} is the display width and @code{D} is the number of decimals.

@code{DOUBLE} without an argument or @code{FLOAT(X)} where 25 <= @code{X}

<= 53 stands for a double-precision floating-point number.

@tindex DOUBLE PRECISION

@tindex REAL

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 (but space

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

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

space for these is 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.

If @code{D} is omitted, the default is 0.  If @code{M} is omitted, the

default is 10.

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

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

Prior to MySQL Version 3.23, the @code{M} argument must include the space

needed for the sign and the decimal point.

@tindex NUMERIC

@item NUMERIC(M,D) [ZEROFILL]

to the current date and time by assigning it a @code{NULL} value.  @xref{Date

and time types}.

A @code{TIMESTAMP} is always stored in 4 bytes.  The @code{M} argument only

affects how the @code{TIMESTAMP} column is displayed.

The @code{M} argument affects only how a @code{TIMESTAMP} column is displayed;

its values always are stored using 4 bytes each.

Note that @code{TIMESTAMP(X)} columns where X is 8 or 14 are reported to

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

Note that @code{TIMESTAMP(M)} columns where @code{M} is 8 or 14 are reported to

be numbers while other @code{TIMESTAMP(M)} 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}.

@xref{DATETIME, , @code{DATETIME}}.

@tindex TIME

@item TIME

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

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. @xref{TIME}.

numbers. @xref{TIME, , @code{TIME}}.

@tindex YEAR

@item YEAR[(2|4)]

and 1970-2069 if you use the 2-digit format (70-69).  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 MySQL Version 3.22.) @xref{YEAR}.

unavailable prior to MySQL Version 3.22.) @xref{YEAR, , @code{YEAR}}.

@tindex NATIONAL CHAR

@tindex NCHAR

@item [NATIONAL] CHAR(M) [BINARY]

A fixed-length string that is always right-padded with spaces to the

specified length when stored. The range of @code{M} is 1 to 255 characters.

specified length when stored. The range of @code{M} is 0 to 255 characters

(1 to 255 prior to MySQL Version 3.23).

Trailing spaces are removed when the value is retrieved. @code{CHAR} values

are sorted and compared in case-insensitive fashion according to the

default character set unless the @code{BINARY} keyword is given.

@code{NATIONAL CHAR} (short form @code{NCHAR}) is the ANSI SQL way to

define that a CHAR column should use the default CHARACTER set.  This is

the default in MySQL.

@code{NATIONAL CHAR} (or its equivalent short form, @code{NCHAR}) is the

ANSI SQL way to define that a @code{CHAR} column should use the default

CHARACTER set.  This is the default in MySQL.

@code{CHAR} is a shorthand for @code{CHARACTER}.

some old applications that depend on the existence of a column but that do not

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{""}. @xref{CHAR}.

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

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

@tindex BOOL

@tindex BIT

Fixed that @code{GRANT/REVOKE ALL PRIVILEGES} doesn't affect

@code{GRANT OPTION}.

@item

Removed extra @code{)} from the output of @code{SHOW GRANTS}.

Removed extra @samp{)} from the output of @code{SHOW GRANTS}.

@item

Fixed problem when storing numbers in timestamps.

@item