MySQL - mubvunzo mune mubvunzo. MySQL: mubvunzo mienzaniso. Midzi MySQL queries

Pari, mumwe munhu anogona kuchengeta kukurumidza kuwedzera digitaalinen mashoko. Uye kubva zvikuru mashoko ichi zvinokosha, zvinokosha kuti uchengeteke mu digitaalinen muchimiro ndisa. In ichi ezvinhu, unogona kushandiswa michina yemazuva ano dzakadai Databases. Vanopa rakavimbika kuchengetera chero digitaalinen ruzivo uye date mukana kunogona kuitwa chero nguva ari panyika. Mumwe ruzivo pasi kufunga kwegadziriro MySQL Databases.

DBMS MySQL - chii ichi?

A ndeyeukama Database utariri hurongwa MySQL ndeimwe zvikuru nevanhu uye raiwanzoshandiswa okuchengetera michina. functionality Its inopfuura muzvinhu zvakawanda zviripo Database. Zvikurukuru, mumwe mukuru zviri ndiko kugona kushandisa midzi MySQL queries.

Naizvozvo, vazhinji mapurojekiti, apo nguva kunokosha uye zvakakodzera inonzi kuita mashoko kuchengetwa, uyewo kuita kunzwisisa mashoko ivhu vari abuda mumwe MySQL Database. Vazhinji zviitiko izvi kuti Websites. Muchiitiko chino, MySQL ari akasimudzira mune Implementation kuti vaduku (dzepaIndaneti, Website, mabhizimisi makadhi uye zvichingodaro. P.) Uye zvinetso zvikuru guru (paIndaneti kunotenga, mashoko kuchengetwa , uye zvichingodaro. D.). Muzviitiko zvacho zvose, kuratidza mashoko web papeji vakashandisa MySQL-mubvunzo. The kukumbira Developers kuedza kuita mikana akauya Database Management System.

Sei zvinofanira kurongwa okuchengetera

For yakakunakira okuchengetera kwaizotevera kubudiswa humboo hazvo akarayira. The date mamiriro kuziva kuti tafura vachatarira akafanana, dzinoshandiswa kuchengetera ruzivo. Database pamatafura muri kuva minda (mbiru) unoenderana nomumwe dzakananga enzvimbo date chinhu.

Somuenzaniso, kana tafura vashandi imwe kambani, ndiko kupfuura nyore mamiriro achava seizvi. Nokuti mushandi mumwe wanamatira akasiyana nhamba, iro unowanzoshandiswa senzira chikuru chinoita kuti tafura. Zvadaro muna tafura akanyorwa pachavo mushandi Data. Inogona kuva chinhu: Full zita, kadhi nhamba, nokuti icho wakaiswa, parunhare, kero uye nezvimwe zvakawanda. Maererano zvinodiwa normalization (6 zvinoitika siyana Databases) uyewo MySQL-queries mudungwe muronga paminda tafura anofanira mabhomba, kureva, kwete kuti enumerations kana mazita. Naizvozvo, kazhinji, iri tafura, pane zvakaparadzana minda okupedzisira zita, wokutanga zita, uye zvichingodaro. D.

Kumusoro chiduku muenzaniso Database tafura mamiriro. Zvisinei, zvichiri kwete zvakazara kundosangana zvinokosha zvinodiwa normalization. In chaiyo hurongwa, anosika chimwezve tafura zvikamu. Naizvozvo, zvinotevera tafura panzvimbo mashoko "Department" mbiru anofanira ane zvinoverengeka madhipatimendi.

Ko mashoko yokuenzanisira

Kuti dzosa mashoko kubva matafura vari Database utariri gadziriro MySQL, boka chaiyo - Select mubvunzo. Kuna Server Database zvakarurama vakaita yakwidzwa, chikumbiro anofanira zvakanaka kuumbwa. mubvunzo mamiriro achiumbwa sezvinotevera. Chero kuwana Database Server rinotanga shoko guru vakasarudzwa. Zvaiva naye akavaka zvose MySQL queries. Mienzaniso anogona kuva akasiyana kunzwisisa, asi nheyo kuvakwa rakafanana chaizvo.

Ipapo vanofanira tsanangurai iyo neminda uchida kusarudza zvinodiwa mashoko. Rinodonongodza minda dzichidzidzisa koma pashure mazano sarudza. Kamwe minda zvose zvaidiwa kunge akanyorwa chikumbiro kutaura tafura chinhu iyo mharidzo kuchaitika norubatsiro mazano kubva uye kutaridzwa zita tafura.

Nokuti zvakabudiswa zvausingakwanisi muna MySQL-queries vari kuwedzera chaiwo dzaishandisa, akapa Database. Nokuti yokuenzanisira unduplicated (rakasiyana) mashoko anoshandiswa muzvichengete vakasiyana, uye kuisa zvinhu - the opareta apo. Somuenzaniso kushandiswawo patafura apa, tinogona kufunga chikumbiro vachirayira mashoko Zita vashandi kushanda dhipatimendi "Sales". mubvunzo mamiriro anotora chimiro sezvo iri tafura pazasi.

Pfungwa imwe nested mubvunzo

Asi chikuru chepfungwa Database, sezvataurwa pamusoro apa, kukwanisa tibate midzi MySQL queries. Zvinofanira kunge? Kubva zita zvine musoro nayo vainzwisisa kuti ichi chinhu chikumbiro zvakapararira munyika akanyatsorongwa zviviri kana kupfuura zvikumbiro. In Nemuromo, nokudzidza peculiarities ose Database panoti kuti MySQL haiiti nhamba MySQL-queries kuti zvinogona nested mu huru mubvunzo. Zvisinei, unogona kuedza mune tsika uye nechokwadi chokuti pashure wechipiri gumi nested mubvunzo mhinduro nguva zvakakomba kuwedzera. Chero zvazvingava, pane tsika pane matambudziko vanofanira kushandisa chaizvo kunzwisisa MySQL-mubvunzo. The chikumbiro kungada vaifanira kubva 3-5 nested hierarchies.

Kuvaka nested queries

Mune Kuongorora iverengwe mashoko, mibvunzo inoverengeka pamusoro apo Sub-queries, uye kana iwe usingagoni kugadzirisa dambudziko kuparadzanise vave nyore pasina complicating maumbirwo anogona kushandiswa. In tsika, Sub-queries zvinoshandiswa kugadzirisa matambudziko akaoma. Kwakadaro mhando matambudziko mamiriro ezvinhu kana asingazivi pachine zvinhu pasi iyo muganhu anokoshesa mamwe zvakabudiswa kuchaitika. Hazvibviri kuti dzipedze zvinetso zvakadaro, kana iwe chete kushandisa dzose MySQL-mubvunzo. In chikumbiro, zvinosanganisira akanyatsorongwa, vachava mitemo kutsvaka kuti kusanduka nenguva kana pachine haagoni kuzivikanwa.

Kana tikafunga tafura kumusoro, zvinotevera muenzaniso uri kunzwisisa basa. Toti tinofanira kuziva mashoko anokosha pamusoro vashandi vari pasi Grishina Grigoriya Grigorevicha, iye musoro rokutengesa. In achiumba mubvunzo hatizivi nhamba yazivikanwa. Saka pakutanga tinofanira kuzviziva. It anoshandisa mubvunzo nyore kuti achawana huru tichitarisa chisarudzo uye achaita mukwanisi chikuru MySQL-mubvunzo. The chikumbiro rinoratidza zvakajeka kuti subquery anopiwa mushandi ID nhamba, mamwe inorondedzera muganhu huru mubvunzo:

Muchiitiko chino, chero zano rinoshandiswa kudzivirira panowanikwa zvikanganiso, kana vashandi pamwe initials akadaro achava mashoma.

zvabuda

Kuti muchidimbu, zvinofanira kucherechedzwa kuti pane zvimwe zvakawanda zvimwe zvinhu kuti zviite zvikuru kuvakwa mubvunzo, sezvo DBMS MySQL - chishandiswa chine simba ine maturusi akasiyana-siyana kuti okuchengetera uye kugadzira.