Ukukhetha iDatha kwiiRanges kwi-SQL

Ukuzisa isigatshana se-WHERE kunye NGEMINYE imeko

ULwimi oluCwangcisiweyo lweeNgxelo (SQL) lunikeza abasebenzisi beenkcukacha ngekhono lokwenza imibuzo eyenziwe ngokwezifiso ukukhipha ulwazi kwiinkcukacha zolwazi. Kwinqaku elingaphambili, sihlolisise ulwazi olususa kwi-database usebenzisa i-SQL SELECT imibuzo . Makhe sandise kule ngxoxo kwaye sihlolisise indlela ongenza ngayo imibuzo ephakamileyo yokufumana idatha ehambelana nemeko ethile.

Makhe siqwalasele umzekelo esekelwe kwi-database yaseNorthwind esetyenziswa ngokuqhelekileyo, esoloko ihamba kunye nemikhiqizo yedatha njengemfundo.

Nantsi ingqungquthela evela kwitheyibhile yomkhiqizo wedatha:

Uluhlu lweMveliso

ProductID	Igama lemveliso	UmthengisiID	UbungakananiPerUnit	Ixabiso lento	UnitsIntock
1	Chai	1	Iibhokisi ezili-10 x 20 iibhegi	18.00	39
2	Tshintsha	1	Iibhola ze-oz 24-12	19.00	17
3	Isiraphu esisikiweyo	1	12 - 550 iibhotile	10.00	13
4	I-Chef Anton's Cajun Seasoning	2	48 - 6 izitya ze-oz	22.00	53
5	I-Chef Anton's Gumbo Mix	2	36 iibhokisi	21.35	0
6	U-Grandm's Boysenberry Usasazeka	3	12 - 8 izitya	25.00	120
7	Amalume aseMal Bob's Organic Omebileyo	3	12 - 1 lb pkgs.	30.00	15

Imibandela elula

Imithintelo yokuqala esiza kuyifaka kumbuzo wethu iquka imeko elula imida. Siyakwazi ukucacisa ezi ziqendu ze-WHERE ye-SELECT, ngokusebenzisa izitatimende zeemeko ezilula ezakhiwe ngabaqhubi abaqhelekileyo, njenge <,>,> =, kunye <=.

Okokuqala, makhe sizame umbuzo olula osivumela ukuba sikhiphe uluhlu lwazo zonke iimveliso kwiziko ledatha eneCandeloPrice elingaphezu kwama-20:

UKUHLOLA I-ProductName, i-UnitPrice KWIIMveliso EZIKHIWO U-UnitPrice> 20.00

Oku kuvelisa uluhlu lweemveliso ezine, njengoko kuboniswe ngezantsi:

UnitName UnitPrice ------- -------- Umqhubi we-Anton's Gumbo Mix 21.35 I-Chef Anton's Cajun Seasoning 22.00 Umama ka-Boysenberry usasazeka 25.00 Amalimi angama-Bob aphekiweyo ama-Pears 30.00

Singasebenzisa kwakhona isigatshana se-WHERE ngexabiso leetambo. Oku kubaluleka ngokulinganisa abalinganiswa kumanani, kunye ne-A emela ixabiso 1 ne-Z ebonisa ixabiso 26. Ngokomzekelo, singabonisa yonke imveliso ngamagama aqala ngo-U, V, W, X, Y okanye i-Z ngolu hlobo lulandelayo:

UKUHLOLA UMSEBENZI WOKUSEBENZA KWEEMveliso EZIKHO UMkhiqizoName> = 'T'

Okuvelisa umphumo:

UmkhiqizoName ------- Amapheya adibeneyo kaMal Bob

Ukubonisa iiRanges usebenzisa iMida

ISAHLUKO SESIFUNDO sisivumela ukuba siphumelele imilinganiselo yeemeko kwixabiso ngokusebenzisa izimo ezininzi. Ngokomzekelo, ukuba sifuna ukuthatha umbuzo wethu ngasentla kwaye sinciphise iziphumo kwimveliso ngamaxabiso phakathi kwe-15.00 no-20.00, sinokusebenzisa le mibuzo elandelayo:

UKUHLOLA I-ProductName, i-UnitPrice KWIIMveliso EZIPHAKATHI KWI-UnitPrice> 15.00 NO-UnitPrice <20.00

Oku kuvelisa umphumo uboniswe ngezantsi:

UnitName UnitPrice ------- -------- Chai 18.00 Iinguqu 19.00

Ukuvakalisa iiRanges phakathi KWAKHO

I-SQL ikwabonelela ngeendlela ezimfutshane phakathi kwe-syntax eyanciphisa inani leemeko esiyidingayo ukuba zifake kwaye yenza ukuba umbuzo ufundeke ngakumbi. Ngokomzekelo, endaweni yokusetyenziswa kwezi zimbini zilapha apha, singachaza umbuzo ofanayo njengoko:

UKUKHETHA UMTHETHO WAMANZI, ISIQEPHU ESIKWELWA KWIIMveliso EZIPHAKATHI KWI-UnitPrice KWI-15.00 NO-20.00

Njengoko kunye nezinye izigatshana zeemeko, NGAPHAKATHI kusebenzisana nemigangatho yeetambo. Ukuba sifuna ukuvelisa uluhlu lwawo onke amazwe aqala ngeV, W okanye X, singasebenzisa umbuzo:

UKUKHETHA UMTHETHO WAMAKHIWO KWEEMveliso EZIKHIWO I-ProductName phakathi "A" kunye ne "D"

Okuvelisa umphumo:

UmkhiqizoName ------- I-Syrup Chai Chang Chef I-Anton's Gumbo Mix Mix I-Anton's Cajun Seasoning

ISAHLUKO SEMHLABA sinxalenye enamandla yeelwimi le-SQL elivumela ukuba ukhawulele iziphumo kwiimpawu eziwela kumacandelo athile. Kuqhelekileyo kusetyenziswe ukunceda ukuchaza ingcamango yezoshishino kwaye kufuneka ibe yinxalenye yesikhokelo sobungcali besicatshulwa.

Kukuninzi kunceda ukufaka amacandelwana aqhelekileyo kwinkqubo egcinwe ukwenza ukuba kufinyeleleke kwabo bangenalo ulwazi lwe-SQL.