6.6: MySQL
NULL, , max_allowed_packet.
, , 1, 0.
ASCII(str)
ASCII- str. 0, str . NULL, str NULL:
mysql> select ASCII("2");
-> 50.
mysql> select ASCII(2);
->50
mysql> select ASCII("dx");
-> 100
ORD(str)
str , , ASCII- : (( ASCII-)*256 + ( ASCII-))[*256 + ASCII- +...]. , ASCII():
mysql> select ORD("2");
-> 50
(N, from_base, to_base).
. N, from_base to_base. NULL, NULL.
N , . - 2, - 36. to_base - , N . N . CONV 64- :
mysql> select CONV(a,16,2);
-> 1010"
mysql> select CONV(6E,18,8);
-> "172"
mysql> select C0NV(-17,10,-18);
-> "-H"
mysql> select CONV(10+10"+'10'+0xa,10,10);
-> "40"
BIN(N)
N, N longlong (BIGINT). CONV(N,10,2). NULL, N NULL:
mysql> select BIN(12);
-> 1100"
OCT(N)
N, N longlong (BIGINT). C0NV(N,10,8). NULL, N NULL:
mysql> select OCT(12);
-> "14"
HEX(N)
N, N longlong (BIGINT). CONV (N,10,16). NULL, N NULL:
mysql> select (255);
-> "FF"
CHAR(N,. . .).
CHAR() , , ASCII- . NULL :
mysql> select CHAR(77,121,83,81,'76');
-> "MySQL"
mysql> select CHAR(77,77.3,'77.3');
-> ""
CONCAT(str1,str2,...).
, . NULL, NULL. , 2 . :
mysql> select CONCAT ("My", "S", QL");
-> "MySQL"
mysql> select CONCAT ("My", NULL, "QL");
-> NULL
mysql> select CONCAT(14.3);
-> '14.3'
CONCAT_WS(separator, str1, str2,...).
CONCAT_WS() CONCAT With Separator ( ) CONCAT(). . , . NULL, NULL. , :
mysql> select CONCAT_WS(,, First name, Second name, Last Name);
-> "First name,Second name,Last Name"
mysql> select CONCAT_WS(,,First name,NULL,Last Name);
-> "First name,Last Name"
LENGTH (str), OCTET_LENGTH(str), CHAR_LENGTH(str) CHARACTER_LENGTH(str)
str:
mysql> select LENGTH("text");
-> 4
mysql> select OCTET_LENGTH("text");
-> 4
, CHAR_LENGTH() .
LOCATE(substr,str), POSITION(substr IN str), LOCATE(substr,str) POSITION(substr IN str)
substr str. substr str, 0:
mysql> select LOCATE("bar", "foobarbar");
-> 4
mysql> select LOCATE("xbar", "foobar");
-> 0
.
LOCATE(substr,str,pos).
substr str, pos. substr str, 0:
mysql> select LOCATE("bar", "foobarbar",5);
-> 7
.
INSTR(str,substr)
LOCATE(), :
mysql> select INSTR("foobarbar", "bar");
-> 4
mysql> select INSTR("xbar", "foobar");
-> 0
.
LPAD(str,len,padstr)
str, padstr. str len . str , len, len . str , len , padstr .
mysql> select LPAD("hi",4,'??');
-> "??hi"
RPAD (str,len,padstr)
LPAD(str,len,padstr), padstr .
mysql> select RPAD("hi",5,'?');
-> "hi???"
LEFT(str,len)
len str:
mysql> select LEFT(foobarbar", 5);
-> "fooba"
.
RIGHT(str,len)
len str:
mysql> select RIGHT("foobarbar", 4);
-> "rbar"
.
SUBSTRING(str,pos,len), SUBSTRING(str FROM pos FOR len) MID(str,pos,len)
len str, pos. , FROM ANSI SQL92:
mysql> select SUBSTRING("Quadratically",5,6);
-> "ratica"
.
SUBSTRING(str,pos) SUBSTRING(str FROM pos)
str, pos:
mysql> select SUBSTRING("Quadratically",5);
-> "ratically"
mysql> select SUBSTRING("foobarbar" FROM 4);
-> "barbar"
.
SUBSTRING_INDEX(str,delim,count)
str, count delim. count , . count , :
mysql> select SUBSTRING_INDEX("www.mysql.com", ".", 2);
-> "www.mysql"
mysql> select SUBSTRING_INDEX(www.mysql.com", ".", -2);
-> "mysql.com"
.
LTRIM(str)
str :
mysql> select LTRIM(" barbar");
-> "barbar"
RTRIM(str)
str :
mysql> select RTRIM("barbar ");
-> "barbar"
.
TRIM([[BOTH|LEADING|TRAILING] [remstr] FROM] str)
str, remstr. BOTH, LEADING TRAILING , BOTH. remstr, . LEADING , TRAILING , a BOTH :
mysql> select TRIM(" bar ");
-> "bar"
mysql> select TRIM(LEADING "x" FROM "xxxbarxxx");
-> "barxxx'
mysql> select TRIM(BOTH "x" FROM "xxxbarxxx");
-> "bar"
mysql> select TRIM(TRAILING "xyz" FROM "barxxyz");
-> "barx"
.
SOUNDEX(str)
soundex- str. , . , , soundex-.
soundex- 4 , SOUNDEX() . SUBSTRING() , soundex-. - . A-Z :
mysql> select SOUNDEX("Hello");
-> "H400"
mysql> select SOUNDEX("Quadratically");
-> "Q36324"
SPACE(N)
, N-:
mysql> select SPACE(6);
-> " "
REPLACE(str, from_str, to_str)
str, from_str to_str:
mysql> select REPLACE("www.mysql.com", "w", "Ww");
-> "WwWwWw.mysql.com"
.
REPEAT(str, count)
, str, count . count <=0, . str count NULL, NULL:
mysql> select REPEAT("MySQL", 3);
-> "MySQLMySQLMySQL"
REVERSE(Str)
str :
mysql> select REVERSE("abc");
-> "cba"
.
INSERT(str, pos, len, newstr)
str , pos len , newstr:
mysql> select INSERT("Quadratic", 3, 4, "What");
-> "QuWhattic"
.
ELT(N,str1,str2,str3,...)
str1, N=1, str2, N=2 . NULL, N , 1, , . ELT() FIELD(), :
mysql> select ELT(1, "ej", "Heja", "hej", "foo");
-> "ej"
mysql> select ELT(4, "ej", "Heja", "hej", "foo");
-> "foo"
FIELD(str,str1,str2,str3,...)
str str1, str2, str3 0, str . FIELD() ELT():
mysql> select FIELD("ej", "Hej", "ej", "Heja", "hej", "foo");
-> 2
mysql> select FIELD("fo", "Hej", "ej", "Heja", "hej", "foo");
-> 0
FIND_IN_SET(str,strlist)
1 N, str strlist, N . , , (,).
, SET, FIND_IN_SET() , . 0, str strlist strlist . NULL, NULL. , :
mysql> SELECT FIND_IN_SET(b",'a,b,c,d');
-> 2
MAKE_SET (bits, str1 str2, ...)
, , (,), , bits.str1 0, str2 1 . NULL str1, str2, ... :
mysql> SELECT MAKE_SET(1,'','b','');
-> ""
mysql> SELECT MAKE_SET(1 | 4,'hello','nice','world');
-> "hello,world"
mysql> SELECT MAKE_SET(0,'a','b','c');
-> ""
EXPORT_SET(bits, on, off, [separator, [number_of_bits]])
, , bit, , on, , , , off. ( separator, ) number_of_bits ( 64):
mysql> select EXPORT_SET(5,'','N',',,4)
-> Y,N,Y,N
LCASE(Str) LOWER(str)
str , ( : ISO-8859-1 Latin1):
mysql> select LCASE("QUADRATICALLY");
-> "quadratically"
.
UCASE(str) UPPER(str)
str , ( : ISO-8859-1 Latin1):
mysql> select UCASE("Hej");
-> "HEJ"
.
LOAD_FILE(file_name)
. ( !), file ( , , ). , max_allowed_packet. , NULL:
mysql> UPDATE table_name SET blob_column=LOAD_FILE(/tmp/picture) WHERE id=1;
MySQL :
mysql> SELECT 1+1";
-> 2
mysql> SELECT CONCAT(2,' test);
-> 2 test
, CONCAT().
, . , , . .