Rorohiko, Pātengi
SQL (momo raraunga): Ripanga
I roto i te ao i teie mahana i reira e he maha nui o ngā taputapu, me ngā hangarau mō te mōhiohio rokiroki. Ko tētahi o nga ara tino noa ko te pātengi raraunga, mo e whakamahi rerekē pūnaha mana. Te whakaaro tikanga rokiroki e he hanganga mārama katoa o nga raraunga me e whakarārangitia i roto i te ripanga motuhake. Ratou, i roto i te tahuri, ngā o te tauwhāiti huanga tīwae momo raraunga.
momo raraunga - he aha te mea te reira?
I teie mahana, i reira e rave rahi whakamāramatanga, whakamārama te ariā o te wā "momo raraunga." Heoi, ia o ratou kua kotahi tikanga noa. Na reira, ko te momo o ngā raraunga taea e murua e whakaritea rite te rōpū raraunga, āhuatanga e ona uara (huru, tau, me ētahi atu) me te hoki tono ngā mahi ki te uara whakaaro.
Ko matamaha Scope o nga momo raraunga. E whakamahia ratou mo te rokiroki e kore anake, engari ano hoki i roto i te hōtaka mō ngā mahi rerekē. A, no te hoahoa hōtaka he whanaketanga whānui, me te whakamahi o ngā momo raraunga taketake ki te huinga motuhake o ngā mahi. Heoi, i runga i kaiwhakamahi e tonu nga momo raraunga taketake. Kei te hāngai SQL-paerewa ano i runga i te whakamahi o te momo tino noa o taketake, engari ki te maha o motuhake tāpiri-ake.
Whakarōpū o momo raraunga
Whakarōpū raraunga i te momo, ko te roa te wa, a ka meinga e te hiahia ki te whakarite i ngā mōhiohio mō te tukatuka ngāwari. Na te pūtake o ngā momo raraunga tīariari hanga rua: pūāhua me te tau.
kua I te pūtake o ratou whakarōpū nāianei kua whakawhanakehia reira, e ngā kuru, arorau, tau tōpū, wāhi mānu tau me ngā momo aho raraunga. rawa e hipokina whakarōpū katoa o te runga ake - SQL. Heoi, i reira e atu tāpiri-mai mo etahi DBMS hou. Ko ētahi o ēnei Oracle me MySQL.
momo raraunga Basic
Whakamahia ka hanga nga papa o huru e te whakatau i nga paerewa reo o te SQL, momo raraunga e wehea ki te 4 ngā akomanga:
- aho;
- hautau;
- uara tselochiselennye;
- rā me te wā uara.
momo raraunga Aho
Ko te rōpū tuatahi o ngā uara ki te rokiroki i tetahi raraunga, māngai rite pūāhua.
E nehenehe te reira pūāhua motuhake, tau, me pukapuka, i roto i to ratou totality ka tukinotia rite te aho i roto i tetahi SQL rapu. Ngā momo o te rārangi ripanga raraunga whakaaturia nei i raro nei, ki te hanga i te rōpū tuatahi.
Char (rahi) | Kei te whakamahia te reira ki te rokiroki aho. Tawhā i roto i te taiapa ka taea ki te whakatika i te roa o te aho penapena. Te rahi mōrahi i roto i paita e taea te whakaturia mo te rarangi - 255. |
VARCHAR (rahi) | Waihoki, ka taea e te momo o mua rokiroki string 255 pūāhua te roa. Heoi, pērā char e te nui e hiahiatia ana o te mahara tohaina mō te pupuri i te uara o tenei momo. Ko, hoki he string tënei o 5 pūāhua, 6 paita o mahara e hiahiatia ana. I roto i te take tuatahi ka te mahara mo te uara kia tīpakohia rite ki tawhā mea. |
KUPU Tiny | Whakamahia ki raraunga toa string ake ki 255 pūāhua. |
KUPU | Whakamahia mō te rokiroki mōhiohio kuputuhi, e kore e te rahi o e nui 65 535 pūāhua. |
ükui | Ko te momo o te raraunga, ko te momo KUPU rite, me te taea ki te pupuri i te mōhiohio kuputuhi pātengi raraunga nei rōrahi taea tae 65.535 pūāhua. Otiia i roto i te mahi e whakamahia ana e ia mō te rokiroki o raraunga oro, pikitia, tuhinga hiko, me pera atu. |
KUPU Waenga | I hangaia te reira i hāngai i runga i te momo o te KUPU, engari ka taea ki a koe rokiroki atu raraunga e tika ana ki te rahi nui ake o runga ki te 16.777.215 o reta ranei tohu. |
ükui Waenga | Whakamahia ki te rokiroki i roto i te pātengi raraunga o ngā tuhinga hiko, e kore e te rahi o e nui te tohu o 16.777.215 pūāhua. |
KUPU ROA | Functionally rite ki te momo o mua, engari ki te kaha mahara nui o runga ki te 4 gigabytes. |
ükui ROA | āhei te reira ki a koutou hoatu i roto i te turanga o buka nui o ngā raraunga (4 294 967 295 pūāhua). |
ENUM (he, b, c, me ētahi atu) | He momo raraunga motuhake whakamahia e te ki te tautuhi i te rārangi o ngā uara taea. 65535 Āhei ki a koutou whakapūtā uara. Rarangi o te momo i roto i te pātai ka taea e riro i te uara kotahi i te huinga i tohua. I roto i te take i reira e waiho te tua nga uara kahore e e tapae i roto i te rārangi i homai i roto i te tepu, ka kia tuhituhia ki te uara kau. |
WHAKARITE | Tautuhi te huinga o ngā uara tika. I roto i te rerekē ki te momo o mua, kei te whakamahia 64 ki te roto i ngā tawhā e kia arawhiti e huānga tetahi rave rahi ranei i te huinga o ngā tohenga. |
Ripanga momo raraunga hautanga
E whakamahia momo raraunga SQL hautanga mō te pupuri tere tau ira. I roto i te mahi, kia rite ki te tikanga, whakaturia te ngā tohu pūtea. Tei runga i te tika e hiahiatia whakamahi tetahi o te whai ake e toru:
Manu (rahi, d) | āhei te reira i roto i tau hautanga tohu pū d. |
HUARUA (rahi, d) | Whakamahia ki te rokiroki tau hautanga ki pū rua. |
Ira (rahi, d) | E rongoa nei i te uara hautanga rite aho. |
Hei tauira, i roto i te pēke tātaitanga tika o te wahi hautanga tae te uara o 8 ranei 10-Kore-Th tohu. e kore e taea te whakamahi i te momo tuatahi e rua i roto i tenei rohe.
E rongoa nei i tohu pūtea i roto i te puka o ngā rārangi nui whakahaere te otinga o ngā raruraru maha. Heoi, i roto i te pā ana ki ngā take pūtea ranei e mau ana i roto i ngā whakahaeretanga o SQL momo raraunga faafariuraa he o faufaa nui. kia tino ki te whakaaro i te momo o ngā tikanga rokiroki me te tukatuka ngā, tonu noho te taua nga raraunga.
momo raraunga tōpū
Tau tōpu - he rōpū motuhake o tau hanga i te tetahi o nga akomanga matua. hāngai momo SQL raraunga tōpū e i runga i te whakamahi o te momo turanga tau tōpū ki etahi toronga o ona āhuatanga.
INT (rahi) | uara tōpū Storage hanga i te whānuitanga o [-2 31; 2 31 -1] |
TINYINT (rahi) | tavini te reira ki tau taonga i roto i te whānuitanga o -128 ki te 127 |
SMALLINT (rahi) | Āhuatanga e nui haere whānuitanga o ngā uara rongoa i roto i te nui o i -32 768 ki te 32 767 |
MEDIUMINT (rahi) | Whakamahia mō te pupuri tau i waenganui i taha -2 te aroaro o Huitanguru 3 2 2 3 -1 |
BIGINT (rahi) | Hipokina te whānuitanga o ngā tau tōpū, timata ki 63, me te mutu -2 2 63 -1 |
Te kōwhiri i te momo matau o raraunga, ka taea e koe te whakaora i te rota o te mahara, ka whakaiti te utu o te wā tūmau e mahi ana e hiahiatia ana SQL-uiui. momo raraunga, ranei, kaua ki o ratou whānuitanga, te whakatau i te nui o te wāhi rokiroki hiahiatia.
Na reira, he nui ngā pātengi raraunga ki te mahara e te whakamahi o awhe nui o ngā huanga arata'i ki te hua i roto i te utu mahara. He mea tika ki āta tātari i te mahi, me te tāutu i ngā take i reira mohiotia whānui āwhiwhiwhi me tikanga o te whakamahi hainatia tau. Ki te he iti te whānuitanga o ngā tohenga whakamahia, a ka waiho i te tau katoa pai, e te mea tika atu ki te whakamahi i waitohu huanga i hanga waitohua.
Ko nga momo o te rā me te wā raraunga
I roto i te ako o nga turanga o momo raraunga SQL, te rā me te wā kei o ngā moni.
Mā te whakamahi i te momo e whai ake nei whakarato painga atu i roto i te whanaketanga o ngā pūnaha e whakawhirinaki i runga i ngā tawhā rangitahi.
DATE | Ko te whakaaro matua - te rā whakatakotoria i roto i te hōputu TAU-MARAMA-DAY ( "YYYY-MM-DD" ranei "yyyy-mm-dd"). E wehea uara angamaheni i na "-", Heoi, kia mahi i tetahi pūāhua atu atu i ngā tau rite ki te whakawehe. |
TIME | taea te reira ki te rokiroki koe te uara pūtau ripanga rangitahi. Kua tohua ngā uara katoa hōputu «HH: mm: ss» |
dateTime | fakatahai te reira i te mahi o nga momo e rua o mua. Ko te hōputu rokiroki ko e whai ake: "yyyy-mm-dd HH: mm: ss». |
waitohuwā | Stores te rā me te wā, he maha countable o hēkona muri mai waenganui po 01/01/1970 me ra ano te uara i tohua. |
TAU (M) | Whakamahia ki te rokiroki i te uara ā-tau i roto i te hōputu rua- ranei wha-mati. |
He aha atu e hiahia ana koe ki te mohio?
Kua systematized katoa o enei momo o te raraunga i roto i te taipitopito i Microsoft. momo raraunga SQL mahi te reira i roto i roto i te taipitopito atu.
Hei tauira, pania e te taipitopito, pehea tohaina nui mahara i roto i paita te whakamahi i ia momo. I muri ui te mōhiohio e wātea ana, ki ngā māmā hoahoa te hanganga o ngā ripanga me te pātengi raraunga katoa e hāngai ana i runga i nga kaha pūmārō o te tūmau.
atatohu Motuhake - korengia
I te tahi taime te whakaoti i te pātengi raraunga i te āhuatanga i reira ka tāpiri koe ngā pūkete ki te tepu te hiahia ki te tomo mōhiohio i roto i tīwae katoa te ngaro. Hoki tenei whakaaro he atatohu motuhake ki te uara kau - korengia, i te mea hei āwhina i roto i te whakamahi i te reo SQL. Momo o tīwae raraunga, e kore e tika i ki kia whakakiia, ka hanga e tohua nga tepu i te kaiwhakahaere, tukua te whakaurunga o ngā uara korenga. kaiwhakahaere te kore i korengia ki te pīmua atu NOT kia kia mahi ki te tohu i te otinga whakahauanga o ngā uara katoa.
atatohu i korengia He kahore momo, engari tohu noa ki te uara whakakahore i roto i nga tepu pātengi raraunga. Na reira, e taea te ngā reira ki tetahi o nga momo i runga ake.
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