MySQL Administrator''''s Bible- P17

MySQL Proxy
A
TABLE A-5
(continued )
Constant Name Context Meaning
BACKEND_TYPE_RW proxy.backends
[x].type
The backend server was defined
with --proxy-backend
-address.
MYSQLD_PACKET_ERR auth.packet:byte()
proxy.response.type
This packet contains an error.
MYSQLD_PACKET_OK auth.packet:byte()
proxy.response.type
This packet was successful.
MYSQLD_PACKET_RAW proxy.response.type This packet contains raw
data.
PROXY_IGNORE_RESULT Return Do not send the results to the
client.
PROXY_SEND_QUERY Return Send the query queue to the
server.
PROXY_SEND_RESULT Return Send the results to the client.
PROXY_VERSION N/A Returns the proxy version, in
hex. 0x00700 corresponds to
version 0.7.0
COM_SLEEP string.byte(packet) This packet contains a sleep
command.
COM_QUIT string.byte(packet) This packet contains a quit
command.
COM_INIT_DB string.byte(packet) This packet contains a init db

command.
COM_QUERY string.byte(packet) This packet contains a query
command.
COM_FIELD_LIST string.byte(packet) This packet contains a field list
command.
COM_CREATE_DB string.byte(packet) This packet contains a create db
command.
COM_DROP_DB string.byte(packet) This packet contains a drop db
command.
COM_REFRESH string.byte(packet) This packet contains a refresh
command.
COM_SHUTDOWN string.byte(packet) This packet contains a shutdown
command.
continued
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A
MySQL Proxy
TABLE A-5
(continued )
Constant Name Context Meaning
COM_STATISTICS string.byte(packet) This packet contains a
statistics command.
COM_PROCESS_INFO string.byte(packet) This packet contains a
process info command.
COM_CONNECT string.byte(packet) This packet contains a
connect command.
COM_PROCESS_KILL string.byte(packet) This packet contains a kill
command.
COM_DEBUG string.byte(packet) This packet contains a

debug command.
COM_PING string.byte(packet) This packet contains a ping
command.
COM_TIME string.byte(packet) This packet contains a time
command.
COM_DELAYED_INSERT string.byte(packet) This packet contains a
delayed insert command.
COM_CHANGE_USER string.byte(packet) This packet contains a
change user command.
COM_BINLOG_DUMP string.byte(packet) This packet contains a
binlog dump command.
COM_TABLE_DUMP string.byte(packet) This packet contains a table
dump command.
COM_CONNECT_OUT string.byte(packet) This packet contains a
connect out command.
COM_REGISTER_SLAVE string.byte(packet) This packet contains a
register slave command.
COM_STMT_CLOSE string.byte(packet) This packet contains a close
command.
COM_STMT_EXECUTE string.byte(packet) This packet contains a
execute command.
COM_STMT_PREPARE string.byte(packet) This packet contains a
prepare command.
COM_STMT_SEND_
LONG_DATA
string.byte(packet) This packet contains a send
long data command.
COM_STMT_RESET string.byte(packet) This packet contains a reset
command.
768

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MySQL Proxy
A
TABLE A-5
(continued )
Constant Name Context Meaning
COM_SET_OPTION string.byte(packet) This packet contains a set
command.
MYSQL_TYPE_NEWDECIMAL proxy.response.
resultset { field
{{type,name}} }
This field has a type of
DECIMAL.
MYSQL_TYPE_TINY proxy.response.
resultset { field
{{type,name}} }
This field has a type of
TINY.
MYSQL_TYPE_SHORT proxy.response.
resultset { field
{{type,name}} }
This field has a type of
SHORT.
MYSQL_TYPE_LONG proxy.response.
resultset { field
{{type,name}} }
This field has a type of
LONG.
MYSQL_TYPE_FLOAT proxy.response.
resultset { field

{{type,name}} }
This field has a type of
FLOAT.
MYSQL_TYPE_DOUBLE proxy.response.
resultset { field
{{type,name}} }
This field has a type of
DOUBLE.
MYSQL_TYPE_NULL proxy.response.
resultset { field
{{type,name}} }
This field has a type of
NULL.
MYSQL_TYPE_TIMESTAMP proxy.response.
resultset { field
{{type,name}} }
This field has a type of
TIMESTAMP.
MYSQL_TYPE_LONGLONG proxy.response.
resultset { field
{{type,name}} }
This field has a type of
LONGLONG.
MYSQL_TYPE_INT24 proxy.response.
resultset { field
{{type,name}} }
This field has a type of INT.
MYSQL_TYPE_DATE proxy.response.
resultset { field
{{type,name}} }

This field has a type of
DATE.
MYSQL_TYPE_TIME proxy.response.
resultset { field
{{type,name}} }
This field has a type of
TIME.
continued
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A
MySQL Proxy
TABLE A-5
(continued )
Constant Name Context Meaning
MYSQL_TYPE_DATETIME proxy.response.
resultset { field
{{type,name}} }
This field has a type of
DATETIME.
MYSQL_TYPE_YEAR proxy.response.
resultset { field
{{type,name}} }
This field has a type of
YEAR.
MYSQL_TYPE_NEWDATE proxy.response.
resultset { field
{{type,name}} }
This field has a type of
NEWDATE.

MYSQL_TYPE_ENUM proxy.response.
resultset { field
{{type,name}} }
This field has a type of
ENUM.
MYSQL_TYPE_SET proxy.response.
resultset { field
{{type,name}} }
This field has a type of SET.
MYSQL_TYPE_TINY_BLOB proxy.response.
resultset { field
{{type,name}} }
This field has a type of
TINY_BLOB.
MYSQL_TYPE_
MEDIUM_BLOB
proxy.response.
resultset { field
{{type,name}} }
This field has a type of
MEDIUM_BLOB.
MYSQL_TYPE_LONG_BLOB proxy.response.
resultset { field
{{type,name}} }
This field has a type of
LONG_BLOB.
MYSQL_TYPE_BLOB proxy.response.
resultset { field
{{type,name}} }
This field has a type of

BLOB.
MYSQL_TYPE_VAR_STRING proxy.response.
resultset { field
{{type,name}} }
This field has a type of
VAR_STRING.
MYSQL_TYPE_STRING proxy.response.
resultset { field
{{type,name}} }
This field has a type of
STRING.
MYSQL_TYPE_GEOMETRY proxy.response.
resultset { field
{{type,name}} }
This field has a type of
GEOMETRY.
MYSQL_TYPE_BIT proxy.response.
resultset { field
{{type,name}} }
This field has a type of BIT.
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MySQL Proxy
A
Further layers in the internal structures are shown in Table A-6. Note that the first five rows
correspond to the internal structures:
■
proxy.socket.client.server
■
proxy.socket.socket.server

■
proxy.connection.backend_ndx
■
proxy.connection.client.default_db
■
proxy.connection.client.send_queue
TABLE A-6
MySQL Proxy Internal Structures
Level 1 Level 2 Level 3 Level 4 Level 5
proxy socket client server
socket server
connection backend_ndx
client default_db
send_queue
username
address
scrambled_password
server thread_id
mysqld_version
scramble_buffer
backends connected_clients
address
state
type
backends pool queue
users
servers
queue
queries type
continued

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A
MySQL Proxy
TABLE A-6
(continued )
Level 1 Level 2 Level 3 Level 4 Level 5
query
response
type
resultset fields
rows
rrrmsg
packet
tokens pdata
text
token_id
token_name
global config proxy lua_script
The
proxy.global.config
structure can be extended to store user-defined variables. For
example, the
rw-splitting.lua
sample script extends the
proxy.global.config
structure
to include:
■
proxy.global.config.rwsplit

■
proxy.global.config.rwsplit.min_idle_connections
■
proxy.global.config.rwsplit.max_idle_connections
MySQL proxy tokens
The proxy tokenizer has a set of tokens that it uses to define parts of a statement. The
‘‘Proxy Tokenizer’’ section earlier showed a few such tokens, including ones for punctuation
(
TK_OBRACE
,
TK_CBRACE
,
TK_DOT
,
TK_STAR
), type (
TK_LITERAL
,
TK_STRING
), and SQL
keywords (
TK_SQL_SELECT
,
TK_SQL_FROM
,
TK_SQL_WHERE
,
TK_SQL_LIKE
).
The tokens in

mysql-proxy
0.6 .0 that are not SQL statement keywords can be found in the
source code file
sql-tokenizer.c
andarelistedinTableA-7.
The SQL keyword tokens in
mysql-proxy
0.6.0 are also found in the source code file
sql-tokenizer.c
and are listed in Table A-8. There are no examples given, because each
token name is the keyword with
TK_SQL_
appended. For example, the token
TK_SQL_ALTER
corresponds to the SQL keyword
ALTER
.
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MySQL Proxy
A
TABLE A-7
MySQL Proxy Tokens
Token Name Example
Punctuation
TK_DOT .
TK_COMMA ,
TK_OBRACE (
TK_CBACE )
TK_SEMICOLON ;

TK_STAR *
Arithmetic
TK_PLUS +
TK_MINUS -
TK_DIV /
TK_LE <=
TK_GE >=
TK_LT <
TK_GT >
TK_EQ =
TK_NE !=
Data Types
TK_STRING ‘‘foo’’
TK_INTEGER 6
TK_FLOAT 1.2
TK_FUNCTION NOW (as in SELECT NOW())
TK_COMMENT /* comment in here */
TK_LITERAL The word after SHOW (as in SHOW TABLES, SHOW
VARIABLES, etc.)
@ and @@ variables Database, table, and column names
continued
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A
MySQL Proxy
TABLE A-7
(continued )
Token Name Example
Functions
TK_BITWISE_AND &

TK_BITWISE_OR |
TK_BITWISE_XOR ˆ
TK_LOGICAL_AND &&
TK_LOGICAL_OR ||
TK_ASSIGN :=
Other
TK_COMMENT_MYSQL ’A MySQL Comment’
TK_UNKNOWN [ ] { }
TABLE A-8
MySQL Proxy SQL Keyword Tokens
SQL Statement Keywords
TK_SQL_ACCESSIBLE
TK_SQL_ACTION
TK_SQL_ADD
TK_SQL_ALL
TK_SQL_ALTER
TK_SQL_ANALYZE
TK_SQL_AND
TK_SQL_AS
TK_SQL_ASC
TK_SQL_ASENSITIVE
TK_SQL_BEFORE
TK_SQL_BETWEEN
TK_SQL_BIGINT
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MySQL Proxy
A
TABLE A-8
(continued )

SQL Statement Keywords
TK_SQL_BINARY
TK_SQL_BIT
TK_SQL_BLOB
TK_SQL_BOTH
TK_SQL_BY
TK_SQL_CALL
TK_SQL_CASCADE
TK_SQL_CASE
TK_SQL_CHANGE
TK_SQL_CHAR
TK_SQL_CHARACTER
TK_SQL_CHECK
TK_SQL_COLLATE
TK_SQL_COLUMN
TK_SQL_CONDITION
TK_SQL_CONSTRAINT
TK_SQL_CONTINUE
TK_SQL_CONVERT
TK_SQL_CREATE
TK_SQL_CROSS
TK_SQL_CURRENT_DATE
TK_SQL_CURRENT_TIME
TK_SQL_CURRENT_TIMESTAMP
TK_SQL_CURRENT_USER
TK_SQL_CURSOR
TK_SQL_DATABASE
TK_SQL_DATABASES
TK_SQL_DATE
continued

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A
MySQL Proxy
TABLE A-8
(continued )
SQL Statement Keywords
TK_SQL_DAY_HOUR
TK_SQL_DAY_MICROSECOND
TK_SQL_DAY_MINUTE
TK_SQL_DAY_SECOND
TK_SQL_DEC
TK_SQL_DECIMAL
TK_SQL_DECLARE
TK_SQL_DEFAULT
TK_SQL_DELAYED
TK_SQL_DELETE
TK_SQL_DESC
TK_SQL_DESCRIBE
TK_SQL_DETERMINISTIC
TK_SQL_DISTINCT
TK_SQL_DISTINCTROW
TK_SQL_DIV
TK_SQL_DOUBLE
TK_SQL_DROP
TK_SQL_DUAL
TK_SQL_EACH
TK_SQL_ELSE
TK_SQL_ELSEIF
TK_SQL_ENCLOSED

TK_SQL_ENUM
TK_SQL_ESCAPED
TK_SQL_EXISTS
TK_SQL_EXIT
TK_SQL_EXPLAIN
TK_SQL_FALSE
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MySQL Proxy
A
TABLE A-8
(continued )
SQL Statement Keywords
TK_SQL_FETCH
TK_SQL_FLOAT
TK_SQL_FLOAT4
TK_SQL_FLOAT8
TK_SQL_FOR
TK_SQL_FORCE
TK_SQL_FOREIGN
TK_SQL_FROM
TK_SQL_FULLTEXT
TK_SQL_GRANT
TK_SQL_GROUP
TK_SQL_HAVING
TK_SQL_HIGH_PRIORITY
TK_SQL_HOUR_MICROSECOND
TK_SQL_HOUR_MINUTE
TK_SQL_HOUR_SECOND
TK_SQL_IF

TK_SQL_IGNORE
TK_SQL_IN
TK_SQL_INDEX
TK_SQL_INFILE
TK_SQL_INNER
TK_SQL_INOUT
TK_SQL_INSENSITIVE
TK_SQL_INSERT
TK_SQL_INT
TK_SQL_INT1
TK_SQL_INT2
continued
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MySQL Proxy
TABLE A-8
(continued )
SQL Statement Keywords
TK_SQL_INT3
TK_SQL_INT4
TK_SQL_INT8
TK_SQL_INTEGER
TK_SQL_INTERVAL
TK_SQL_INTO
TK_SQL_IS
TK_SQL_ITERATE
TK_SQL_JOIN
TK_SQL_KEY
TK_SQL_KEYS

TK_SQL_KILL
TK_SQL_LEADING
TK_SQL_LEAVE
TK_SQL_LEFT
TK_SQL_LIKE
TK_SQL_LIMIT
TK_SQL_LINEAR
TK_SQL_LINES
TK_SQL_LOAD
TK_SQL_LOCALTIME
TK_SQL_LOCALTIMESTAMP
TK_SQL_LOCK
TK_SQL_LONG
TK_SQL_LONGBLOB
TK_SQL_LONGTEXT
TK_SQL_LOOP
TK_SQL_LOW_PRIORITY
TK_SQL_MASTER_SSL_VERIFY_SERVER_CERT
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MySQL Proxy
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TABLE A-8
(continued )
SQL Statement Keywords
TK_SQL_MATCH
TK_SQL_MEDIUMBLOB
TK_SQL_MEDIUMINT
TK_SQL_MIDDLEINT
TK_SQL_MINUTE_MICROSECOND

TK_SQL_MINUTE_SECOND
TK_SQL_MOD
TK_SQL_MODIFIES
TK_SQL_NATURAL
TK_SQL_NO
TK_SQL_NOT
TK_SQL_NO_WRITE_TO_BINLOG
TK_SQL_NULL
TK_SQL_NUMERIC
TK_SQL_ON
TK_SQL_OPTIMIZE
TK_SQL_OPTION
TK_SQL_OPTIONALLY
TK_SQL_OR
TK_SQL_ORDER
TK_SQL_OUT
TK_SQL_OUTER
TK_SQL_OUTFILE
TK_SQL_PRECISION
TK_SQL_PRIMARY
TK_SQL_PROCEDURE
TK_SQL_PURGE
TK_SQL_RANGE
continued
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MySQL Proxy
TABLE A-8
(continued )

SQL Statement Keywords
TK_SQL_READ
TK_SQL_READ_ONLY
TK_SQL_READS
TK_SQL_READ_WRITE
TK_SQL_REAL
TK_SQL_REFERENCES
TK_SQL_REGEXP
TK_SQL_RELEASE
TK_SQL_RENAME
TK_SQL_REPEAT
TK_SQL_REPLACE
TK_SQL_REQUIRE
TK_SQL_RESTRICT
TK_SQL_RETURN
TK_SQL_REVOKE
TK_SQL_RIGHT
TK_SQL_RLIKE
TK_SQL_SCHEMA
TK_SQL_SCHEMAS
TK_SQL_SECOND_MICROSECOND
TK_SQL_SELECT
TK_SQL_SENSITIVE
TK_SQL_SEPARATOR
TK_SQL_SET
TK_SQL_SHOW
TK_SQL_SMALLINT
TK_SQL_SPATIAL
TK_SQL_SPECIFIC
TK_SQL_SQL

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MySQL Proxy
A
TABLE A-8
(continued )
SQL Statement Keywords
TK_SQL_SQL_BIG_RESULT
TK_SQL_SQL_CALC_FOUND_ROWS
TK_SQL_SQLEXCEPTION
TK_SQL_SQL_SMALL_RESULT
TK_SQL_SQLSTATE
TK_SQL_SQLWARNING
TK_SQL_SSL
TK_SQL_STARTING
TK_SQL_STRAIGHT_JOIN
TK_SQL_TABLE
TK_SQL_TERMINTED
TK_SQL_TEXT
TK_SQL_THEN
TK_SQL_TIME
TK_SQL_TIMESTAMP
TK_SQL_TINYBLOB
TK_SQL_TINYINT
TK_SQL_TINYTEXT
TK_SQL_TO
TK_SQL_TRAILING
TK_SQL_TRIGGER
TK_SQL_TRUE
TK_SQL_UNDO

TK_SQL_UNION
TK_SQL_UNIQUE
TK_SQL_UNLOCK
TK_SQL_UNSIGNED
TK_SQL_UPDATE
continued
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A
MySQL Proxy
TABLE A-8
(continued )
SQL Statement Keywords
TK_SQL_USAGE
TK_SQL_USE
TK_SQL_USING
TK_SQL_UTC_DATE
TK_SQL_UTC_TIME
TK_SQL_UTC_TIMESTAMP
TK_SQL_VALUES
TK_SQL_VARBINARY
TK_SQL_VARCHAR
TK_SQL_VARCHARACTER
TK_SQL_VARYING
TK_SQL_WHEN
TK_SQL_WHERE
TK_SQL_WHILE
TK_SQL_WITH
TK_SQL_WRITE
TK_SQL_X509

TK_SQL_XOR
TK_SQL_YEAR_MONTH
TK_SQL_ZEROFILL
Summary
In this appendix you have learned how to use the MySQL Proxy, including:
■ Using multiple backends with MySQL Proxy
■ How MySQL Proxy’s default round-robin connection logic works
■ A brief Lua tutorial
■ How MySQL Proxy tokenizes queries
■ Query injection with MySQL Proxy
■ Reference material for more advanced MySQL Proxy scripting
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Functions and Operators
IN THIS APPENDIX
Using aggregation functions
Using bitwise operators
Compressing and encrypting
data
Testing, logic, and control flow
Using server-level functions
Working with data types
T
his appendix contains the functions and operators available in
MySQL, including whether they are an SQL Standard or a MySQL
Extension.
Using Aggregation Functions
Aggregation functions take a single expression as an argument
but may take input from many rows; they are row-wise functions.
For example, the

AVG(expr)
function takes a simple average
(the sum divided by the count):
mysql> CREATE TABLE nums (num TINYINT);
Query OK, 0 rows affected (0.09 sec)
mysql> INSERT INTO nums (num) VALUES (1),(2),(3);
Query OK, 3 rows affected (0.48 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> select AVG(num) FROM nums;
+----------+
| AVG(num) |
+----------+
| 2.0000 |
+----------+
1 row in set (0.03 sec)
Although aggregate functions work on expressions that encompass
one or more rows, they only take one expression as an
argument. For example, the syntax of
AVG(expr)
does not allow
for the following:
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B
Functions and Operators
mysql> SELECT AVG(1,2,3);
ERROR 1064 (42000): You have an error in your SQL syntax; check the
manual that corresponds to your MySQL server version for the
right syntax to use near ’2,3)’ at line 1
One exception to this rule is that COUNT(DISTINCT expr) can take multiple

arguments.
When
expr
evaluates as
NULL
, for example when there are no rows that match, most aggre-
gation functions return
NULL
. Functions that return 0 when
expr
evaluates as
NULL
are
COUNT(*)
,
COUNT(expr)
,
COUNT(DISTINCT expr)
,
BIT_OR
,and
BIT_XOR
.
Bug
T
here is one function that returns an unexpected result:
BIT_AND(NULL)
:
mysql> SELECT BIT_AND(NULL);
+----------------------+

| BIT_AND(NULL) |
+----------------------+
| 18446744073709551615 |
+----------------------+
1 row in set (0.00 sec)
For the curious,
18446744073709551615
is a 63-bit string where each bit is 1. This has been
reported as MySQL bug 37754 and can be seen at:
/>id=37754
.
Table B-1 lists the aggregate functions and a brief description of each one.
Using Bitwise Operators
MySQL extends standard SQL with special functions for bits. Bitwise operators implicitly cast
arguments to
UNSIGNED BIGINT
. This has the most noticeable effect on bit inversion (∼):
mysql> SELECT 5,∼5,BIN(5),BIN(∼5)\G
*************************** 1. row ***************************
5: 5
∼5: 18446744073709551610
BIN(5): 101
BIN(∼5): 11111111111111111111111111111111111111111111111111111111111
11010
1 row in set (0.00 sec)
Aggregation functions for bits are listed in Table B-1.
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Functions and Operators
B

TABLE B-1
Aggregation Functions
Function Syntax Standard
SQL?
Description
AVG(expr) Yes Simple average; SUM/COUNT.
BIT_AND(expr) No Bitwise AND; returns true if all rows are true and false if
any rows are false.
BIT_OR(expr) No Bitwise OR; returns true if any row is true; returns false if
all rows are false.
BIT_XOR(expr) No Bitwise XOR; a pair where exactly one value is true
returns true; all other pairs will return false. More than 2
rows are done commutatively.
COUNT(expr)
COUNT(*)
COUNT(DISTINCT expr)
Yes
Yes
Yes
Returns a count of all non-NULL values of expr.
COUNT(*) returns a count of all rows.
COUNT(DISTINCT expr) returns a count of how many
rows contain different values for expr.
GROUP_CONCAT(expr) No Concatenates non-NULL values, separated by a comma
by default.
MAX(expr) Yes Returns the maximum value of expr.
MIN(expr) Yes Returns the minimum value of expr.
STD(expr) No Nonstandard SQL equivalent to STDDEV_POP(expr).
STDDEV_POP(expr) Yes Population standard deviation. Same as
SQRT(VAR_POP(expr)).

STDDEV_SAMP(expr) Yes Sample standard deviation. Same as
SQRT(VAR_SAMP(expr)).
STDDEV(expr) No Nonstandard SQL equivalent to STDDEV_POP(expr).
SUM(expr) Yes Returns the sum of all values of expr.
VAR_POP(expr) Yes Population standard variance. This is calculated by taking
the average of the square of the differences between
each value and the average value.
VAR_SAMP(expr) Yes Population standard variance. This is calculated by taking
the sum of the square of the differences between each
value and the average value, and dividing by the number
of values (rows) minus one.
VARIANCE(expr) No Nonstandard SQL equivalent to VAR_POP(expr).
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B
Functions and Operators
Table B-2 lists the bit functions and their descriptions.
TABLE B-2
Bit Functions
Function
Syntax
Standard
SQL?
Description
& No Bitwise AND, returns true when both bit positions are true
∼ No Bit inversion (unary operator)
| No Bitwise OR, returns true when either or both bit positions are true
ˆ No Bitwise XOR, returns true when exactly one bit position is true
<< No Shifts to the left
>> No Shifts to the right

BIT_COUNT No Returns the number of bits that are set
Combining multiple statements
Much like basic arithmetic operators (such as + - * / ), these bitwise operators can be combined
into longer statements, which are then parsed using precedence rules.
Precedence from highest to least is shown in Table B-3.
TABLE B-3
Bit Operator Precedence
Operator(s) Level of Precedence
∼ Highest
ˆ
<< >>
&
| Lowest
Let’s walk through an example:
mysql> SELECT 5 | 2
ˆ
7<<3|4&6;
+------------------------+
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