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MySQLHe aha nā ʻano ʻikepili i kākoʻo ʻia?MySQLNā kikoʻī o nā ʻano ʻikepili ma
Nā ʻano ʻikepili MySQL
ʻO nā ʻano o nā kahua ʻikepili i wehewehe ʻia ma MySQL he mea koʻikoʻi loa ia i ka optimization o kāu waihona.
Kākoʻo ʻo MySQL i nā ʻano ʻano like ʻole, hiki ke hoʻokaʻawale ʻia i ʻekolu mau ʻāpana: helu, lā / manawa, a me nā ʻano string (character).
ʻAno helu
MySQL waihonaKākoʻo ʻia nā ʻano ʻikepili helu SQL maʻamau a pau.
Aia kēia mau ʻano i nā ʻano ʻikepili helu koʻikoʻi (INTEGER, SMALLINT, DECIMAL, a me NUMERIC), a me nā ʻano ʻikepili helu (FLOAT, REAL, a me DOUBLE PRECISION).
ʻO ka huaʻōlelo INT he synonym no INTEGER a ʻo ka huaʻōlelo DEC he synonym no DECIMAL.
ʻO ka ʻano ʻikepili BIT e paʻa i nā waiwai kahua bit a kākoʻo i nā papa MyISAM, MEMORY, InnoDB, a me BDB.
Ma ke ʻano he hoʻonui i ka maʻamau SQL, kākoʻo pū ʻo MySQL i nā ʻano integer TINYINT, MEDIUMINT, a me BIGINT.Hōʻike ka papa ma lalo i ka waiho ʻana a me ka laulā e pono ai no kēlā me kēia ʻano integer.
| ʻAno | nui | laulā (kaulima ʻia) | laulā (ʻaʻole pūlima ʻia) | Hoʻohana |
|---|---|---|---|---|
| TINYINT | 1 byte | (-128, 127) | (0, 255) | helu helu liʻiliʻi |
| LIILII | 2 byte | (-32 768, 32 767) | (0, 65 535) | waiwai helu nui |
| MEDIUMINT | 3 byte | (-8 388 608, 8 388 607) | (0, 16 777 215) | waiwai helu nui |
| INT a i ʻole INTEGER | 4 byte | (-2 147 483 648, 2 147 483 647) | (0, 4 294 967 295) | waiwai helu nui |
| NUI | 8 byte | (-9 233 372 036 854 775 808, 9 223 372 036 854 775 807) | (0, 18 446 744 073 709 551 615) | nui loa ka huina helu |
| LELE | 4 byte | (-3.402 823 466 E+38, -1.175 494 351 E-38), 0, (1.175 494 351 E-38, 3.402 823 466 351 E+38) | 0, (1.175 494 351 E-38, 3.402 823 466 E+38) | hoʻokahi pololei waiwai kiko lana |
| papalua aku | 8 byte | (-1.797 693 134 862 315 7 E+308, -2.225 073 858 507 201 4 E-308), 0, (2.225 073 858 507 201 4 E-308 1.797 693 E-134), 862, (315 7 308 XNUMX XNUMX XNUMX E-XNUMX, XNUMX XNUMX) | 0, (2.225 073 858 507 201 4 E-308, 1.797 693 134 862 315 7 E+308) | pololei pālua waiwai kiko lana |
| OLELO HOOLAHA | No DECIMAL(M,D), inā M>D, ʻo ia ka M+2 a i ʻole he D+2 | pili i nā waiwai o M a me D | pili i nā waiwai o M a me D | waiwai decimal |
ʻano lā a me ka manawa
ʻO nā ʻano lā a me nā manawa e hōʻike ana i nā waiwai manawa ʻo DATETIME, DATE, TIMESTAMP, TIME, a me YEAR.
Loaʻa i kēlā me kēia ʻano manawa ke ʻano o nā waiwai kūpono a me kahi waiwai "zero", i hoʻohana ʻia i ka wā e kuhikuhi ana i kahi waiwai kūpono ʻole ʻaʻole hiki i MySQL ke hōʻike.
Loaʻa i ka ʻano TIMESTAMP kahi hiʻohiʻona hoʻopiʻi auto-pono e wehewehe ʻia ma hope.
| ʻAno | nui (byte) | laulā | hōʻano | Hoʻohana |
|---|---|---|---|---|
| ʻO DATE | 3 | 1000-01-01/9999-12-31 | YYYY-MM-DD | waiwai lā |
| TIME | 3 | ‘-838:59:59'/'838:59:59' | HH: MM: SS | waiwai manawa a lōʻihi paha |
| MAKAHIKI | 1 | 1901/2155 | YYYY | makahiki waiwai |
| KĀNĀWAI | 8 | 1000-01-01 00:00:00/9999-12-31 23:59:59 | YYYY-MM-DD HH: MM: SS | Ua hui pū ʻia ka lā a me ka manawa |
| KUMUHANAWAI | 4 | 1970-01-01 00:00:00/2037 年某时 | YYYYMMDDHHMMSS | helu hui la a me ka manawa, timestamp |
ʻAno kaula
Hōʻike nā ʻano string i CHAR, VARCHAR, BINARY, VARBINARY, BLOB, TEXT, ENUM, a me SET.Hōʻike kēia ʻāpana i ka hana ʻana o kēia mau ʻano a pehea e hoʻohana ai i nā nīnau.
| ʻAno | nui | Hoʻohana |
|---|---|---|
| KAU | 0-255 byte | kaula lōʻihi paʻa |
| VARCHAR | 0-65535 paika | kaula lōʻihi lōʻihi |
| TINYBLOB | 0-255 byte | ʻO ke kaula binary a hiki i ka 255 huapalapala |
| TINYTEXT | 0-255 byte | kaula kikokiko pōkole |
| BLOBA | 0-65 535 bytes | ʻikepili kikokikona lōʻihi ma ke ʻano binary |
| KAUA | 0-65 535 bytes | ʻikepili kikokikona lōʻihi |
| BLOB MEDIUM | 0-16 777 215 bytes | ʻikepili kikokikona lōʻihi ma ke ʻano binary |
| HAAWINA KULA | 0-16 777 215 bytes | ʻikepili kikokikona lōʻihi waena |
| LONGBLOB | 0-4 294 967 295 paita | ʻikepili kikokikona nui loa ma ke ʻano binary |
| LONGTEXT | 0-4 294 967 295 paita | ʻikepili kikokikona nui loa |
Ua like nā ʻano CHAR a me VARCHAR, akā mālama ʻia a hoʻihoʻi ʻokoʻa.He ʻokoʻa nō hoʻi lākou ma ke ʻano o ko lākou lōʻihi kiʻekiʻe a inā paha e mālama ʻia nā wahi hope.ʻAʻole hoʻololi ʻia ka hihia i ka wā o ka mālama ʻana a i ʻole ke kiʻi ʻana.
Ua like nā papa BINARY a me VARBINARY me CHAR a me VARCHAR, koe wale nō nā kaula binary ma kahi o nā kaula binary ʻole.ʻO ia hoʻi, loaʻa iā lākou nā kaula byte ma mua o nā kaula kiko.ʻO kēia ke kumu ʻaʻohe o lākou ʻano, a ʻo ka hoʻonohonoho ʻana a me ka hoʻohālikelike ʻana e pili ana i nā helu helu o nā bytes waiwai kolamu.
ʻO ka BLOB kahi mea nui binary hiki ke mālama i ka nui o ka ʻikepili.Aia nā ʻano BLOB 4: TINYBLOB, BLOB, MEDIUMBLOB a me LONGBLOB.ʻOkoʻa wale lākou i ka lōʻihi loa o ka waiwai i hiki iā lākou ke paʻa.
Aia nā ʻano TEXT 4: TINYTEXT, TEXT, MEDIUMTEXT a me LONGTEXT.Hoʻopili kēia i nā ʻano BLOB 4, me ka lōʻihi like ʻole a me nā koi mālama.
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