Ho Fumana Data ho tswa ho Lithebula Tse Ngata le Likopano tsa SQL Tse ka Hare

Kahare o kenela tlhahisoleseding e khutlisetsang e hlahang boitsebisong ba mabeli kapa ho feta

Likamano tsa ka hare ke tsona tse sebelisoang hangata ho SQL. Ba khutlisa feela tlhahisoleseding e teng litabeng tse peli kapa tse fetang tsa databases. Boemo bo kopantsoeng bo etsa qeto ea hore na ke litlaleho life tse kopanetsoeng hammoho 'me ho boleloa hore na ho na le serapa sa WHERE. Ka mohlala, haeba u hloka lethathamo la likoloi tsa koloi / koloi moo koloi le mokhanni li leng teng motseng o le mong, potso e latelang ea SQL e phetha mosebetsi ona:

SELECT lastname, firstname, tag FROM HO bakhanni ba likoloi, likoloi HA HO BA bakhanni.banang = likoloi

Mona ke liphello:

lebitso la hau la pele
----------- ------------ ----
Baker Roland H122JM
Smythe Michael D824HA
Smythe Michael P091YF
Jacobs Abraham J291QR
Jacobs Abraham L990MT

Hlokomela hore liphello ke sona se neng se batloa. Hoa khoneha ho ntlafatsa ts'ebetsong ka ho bonts'a litekanyetso tse eketsehileng ho SELELELE seo. Nka hore ts'ebetso ea pele e bapisoa le bakhanni ba likoloi tseo ba sa li lumelloang ho li khanna (bakhanni ba literaka ba ea likoloi le ka tsela e fapaneng). U ka sebelisa potso e latelang ho rarolla bothata bona:

SELECT lastname, firstname, tag, likoloi.class HO tsoa ho bakhanni, likoloi HA HO ba bakhanni.location = likoloi.haho ​​le ba khanna.class = likoloi.class

Mohlala ona o totobatsa tafole ea mohloli bakeng sa tšobotsi ea sehlopha ka karolong ea SELECT hobane sehlopha se na le moelelo-se bonahala liphatleng tse peli. Hangata khoutu e ne e totobatsa hore na mohala ofe oa tafole o lokela ho kenngoa liphellong tsa lipotso. Tabeng ena, ha e etse phapang, kaha lihlopha li tšoana mme li kopantsoe ho sebelisa equijoin. Leha ho le joalo, haeba litšiea li na le data e fapaneng, phapang ena e tla ba ea bohlokoa. Mona ke liphetho tsa potso ena:

tloaelo ea lebitso la lebitso la hau
---------- ------------ ---- ------
Baker Roland H122JM Car
Smythe Michael D824HA Truck
Jacobs Abraham J291QR Koloi

Melao e lahlehileng e ne e arolelana Michael Smythe ho koloi le Abraham Jacobs ho ea terakeng, likoloi tseo ba neng ba sa li lumelloa ho khanna.

U ka boela ua sebelisa mahlakore a kahare ho kopanya data ho tloha litafole tse tharo kapa ho feta .