Te mahi ki te pātengi raraunga: He aha he tono

He aha te mea te "tono"? He aha te tikanga auraa e te uiui i roto i te pātengi raraunga? He aha e nga tono e kua tonoa ki te pātengi raraunga? I raro i te tono Poiete te supply o etahi tikanga, kia rite ki nei e whakahoki te pātengi raraunga, me te whakarato i ngā mōhiohio o te moni. ie i reira ka tono etahi tikanga / raraunga e i tīpakohia te mōhiohio e tika ana kei te ka tuku ki te taha kiritaki / ranei tomo ki te pātengi raraunga. Ko te whakahoki ki te pātai "he aha te mea te ahanoa, te tono", ka tino ako koe i tenei tuhinga.

Aha uiui ki te pātengi raraunga?

Me hoatu te whakahoki ki te pātai o te mea te tono kore anake, engari ano hoki i runga i te pātai, he aha he uiui. E tika ana ki te tiki i te kōrero rongoa e te i roto i te pātengi raraunga ratou. Mämä noa iho, e hangaia te uiui pātengi raraunga ki te tiki i te kōrero e hiahiatia ana i roto i ētahi wā. Ratou whakaaro e taea e tino rerekē: kia waiho reira e tika ana ki te tāutu i rite te kiritaki o te pareparenga i runga i te pae tuatoru-rōpū, ranei ki te tāutu i rite te ipurangiroto kaimahi, ranei ki te whiwhi mōhiohio e pā ana ki te āhua o te kōtaha i runga i te pae tukutuku o te kēmu.

He aha e nga wāhanga o te uiui, ko te?

tonu tatou ki te whakautu ki te pātai: He aha he tono. whakamahia SQL te ki te tuhituhi uiui. Tika i ki kia rua anake ngā wāhanga: Tīpakohia me MEI. Otiia motu i ratou e taea te whakamahi me te whakamahia e te maha o te tahi atu kapa e tāpiri whakaritenga hou mō te kōwhiringa raraunga me te āta ki te whakaatu. Enei tono i roto i te pātengi raraunga ki te whiwhi i te tino hāngai ana ngā mōhiohio i te rorohiko: koe hiahia ki kitea te wahi reira ko te tahi mea ki te titiro hoki. hiahiatia i ngā wāhanga tino rongonui te i muri i te hea. Hea e hāngai ana, i roto i te tikanga ki te whakatakotoria tikanga motuhake mo te kōwhiringa o ngā raraunga. Hei tauira, ka taea e koe te whakapūtā te tau tāututanga, te rā o te whanau atu mōhiohio ranei e he ahurei, me e kia tautuhi i te tangata.

Te paturaa i te uiui

Tetahi tono kua he tino aroākapa o te hanganga, i taea e kore ofati. Hoki kia puta he hapa. Ka te hanga e faataa i runga i te pūtake o te uiui ohie ki toru wāhanga. Tuatahi i reira e Tīpakohia, MEI, a hea. Ka taea te pato ngā e rua reta nui, me te iti, e kore hoki te pāngia mahia. Otiia rite ki nga tikanga o te ritenga, kei te tuhituhi ngā katoa ki te pukapuka whakapaipai me nga tikanga e hiahiatia ana, te ingoa o te tepu, me te mea ki te iti. A pera atu ngāwari ki te whakatere te wā e tirotiro waehere. E hoki ki te waehere, kia korero koutou motu, e te kawenga mō te aha.

Hanga he uiui, rite ki te tikanga, e kore e rere ke i mahi i roto i ngā tūmomo whanaketanga ngā taiao. Na, e tu ana i roto i mua o koutou he pātai: "He aha he tono mō te whai wāhi» ranei tetahi atu taiao whanaketanga, a taea e koe mohio e ka tae mai i te mau pahonoraa i homai i roto i tenei tuhinga ki a ratou katoa.

tono raraunga Basic

Ko te wāhanga wāhanga matua, pera whakahuatia mua, e rua anake:

• WHIRIWHIRI I [1 mea ki te mea e hiahia ana koe 2, e hiahia ana koe 3] - whakamahia ki te whakapūtā te mea mōhiohio e hiahiatia ana te. E ka whakawhitia ai i te pātengi raraunga ki te hōtaka ki nei kei te mahi i te kaiwhakamahi.
• MAI [tepu i nei e riro raraunga] - whakapūtā he iti te raraunga e hiahiatia ana, a ka hiahia tonu ki te tohu i reira kia ratou kia tangohia. E kore e rongoa i te pātengi raraunga tika raraunga, me te tepu e kua te raraunga. Ka taea e whai i te taua tīwae o raraunga ki te karo i tenei te papa rerekē, me te whakamahia ki te whakapūtā te wahi e tangohia ai.

kōrero atu me ngā mahi rōpū tono

Hei whakapai ake i to koutou hua rapu me te whakarato mōhiohio i runga i te whakamahi o te mōhiohio riro kē whakahau atu:

• Hea [ngā kupu rapu] - whakamahia ki te kōmaka i te mōhiohio e tika ana e pā ana ki te tikanga paearu motuhake.
• whakamahia te ki te whakawhāiti i te maha o ngā rārangi e e ka tangohia i te tepu - Tuhinga [tau].
• GROUP BY [uiui tawhā] - Kei te whakamahia ki te rōpū te mōhiohio riro i te pātengi raraunga. Ko te rōpū, ko te kore e taea te tukua tetahi mōhiohio, engari anake i roto i te rahi ki, a he te taua momo. Hoki ētahi atu kōrero e taea e kitea e koe i roto i na roto i te imiraa i te i te tuhinga motuhake i runga i te GROUP BY. ngā mahi rōpū i roto i te uiui hangaia ki te whakapai ake i te ahua o te mōhiohio me tona aroātanga nui.
• UNION [tono] whakamahia te ki te hoatu i te subquery tono motuhake. A, no te riro koe kia hiahiatia te nui tika nui o ngā mōhiohio kia me taua kōwhiringa.
• Penei ano "" Kei te whakamahia ki te tirohia mēnā hāngai te kanohi ki te tono o te tetahi raraunga rahi. Na, me ona awhina, ka taea e koe te rapu i te tangata nei utu vymeryat ono tau.

tauira

Ko te māramatanga raruraru o tuhituhia, kahore he tauira hāngai tenei i roto ano. Otiia e kore e taea e ara te tauira kotahi whakamārama katoa, a ka whai koe ki te kitea te rota o te mōhiohio i mua ka taea ki te taa i te whai wāhitanga ngā SQL whakaekea katoa koutou:

Tīpakohia Ingoa, ProductNumber, ListPrice AS Price

MEI Production.Product

HEA ProductLine = 'R'

whakaekea Poroporo ahau te waehere runga ake. Tuatahi, i reira te mea he kōwhiringa o te raraunga e tika ana: te ingoa, te tau hua me nga utu whārangi puka. Na whakaaturia te whārangi utu e i te ingoa paku rerekē - he "utu". Ko te raraunga ki te tangohanga o i te pātengi raraunga "Products" i te tepu "Hua". I roto i te whānui, whakapūtā kore he e tika ana te pātengi raraunga, ki te e mahi koe ki tetahi anake, e mau ka tukua te tono. Otiia ki te mea i te torutoru turanga, ka kia mohio ki te tautuhi i, hoatu te meka e te rorohiko noa e kore e matau ki nei kōrero koe, ranei ara wareware koutou tono, a ka whakaputa i te hapa. Ko te rārangi tuatoru tohu e te putanga ko kore te mōhiohio katoa, ko te kotahi anake e haere i roto i te rārangi o "P" hua. E mutu te tuhinga poto, i muri i te tai'oraa koutou matau inaianei, he aha he uiui.