Yi amfani da SQL COUNT don sake dawowa da kewayon bayanai
Sakamakon tambayoyin yana da muhimmin ɓangare na Harshen Query Structured (SQL). Yana dawo da bayanan da ya dace akan takamaiman sharudda daga wani bayanin sirri. Zaka iya amfani da tambayoyin SQL - ciki har da aikin COUNT () - don samun duk bayanai daga wani asusun.
Ayyukan SQL COUNT () yana da amfani musamman saboda yana ba ka damar ƙididdige bayanan bayanai bisa ga ka'idodin mai amfani-kayyade. Zaka iya amfani da shi don ƙidaya duk rubutun a cikin tebur, ƙididdiga dabi'u masu mahimmanci a cikin wani shafi, ko ƙidaya yawan lokutan rikodi na faruwa wanda ya dace da wasu sharuddan.
Wannan labarin yana duba komai akan kowane abu.
Misalai suna dogara ne akan tushen Arewawindow wanda ake amfani dasu, wanda ke amfani dasu tare da samfurori na bayanai don amfani da su azaman koyawa.
Ga wani samfurin daga database na Teburin samfurin:
| ProductID | Sunan Sunan | SupplierID | YawanTaɗaya | UnitPrice | UnitsInStock |
|---|---|---|---|---|---|
| 1 | Chai | 1 | 10 kwalaye x 20 bags | 18.00 | 39 |
| 2 | Chang | 1 | 24 - 12 tabarbalan gas | 19.00 | 17 |
| 3 | Sugar Aniseed | 1 | 12 - 550 ml kwalabe | 10.00 | 13 |
| 4 | Chef Anton na Cajun Seasoning | 2 | 48 - 6 na kwalba | 22.00 | 53 |
| 5 | Chef Anton's Gumbo Mix | 2 | 36 kwalaye | 21.35 | 0 |
| 6 | Grandma ta Boysenberry yada | 3 | 12 - 8 oz kwalba | 25.00 | 120 |
| 7 | Uncle Bob's Organic Dried Pears | 3 | 12 - 1 lb pkgs. | 30.00 | 15 |
Ƙididdiga Bayanan a cikin Allon
Abinda ya fi dacewa shi ne ƙidaya yawan adadin littattafai a cikin tebur. Idan kana so ka san adadin abubuwan da ke cikin teburin kayan aiki, yi amfani da wannan tambaya:
BABI COUNT (*)
FROM samfur;
Wannan tambaya ya koma lambar layuka a teburin. A cikin wannan misali, yana da 7.
Ƙididdigar Ƙididdigar Ɗaukaka a cikin Shafin
Hakanan zaka iya amfani da aikin COUNT don gane yawan lambobin da ke cikin wani shafi. A misali, idan kana so ka gano adadin masu samar da kayayyaki waɗanda samfurori sun bayyana a cikin sashen samarwa, za ka iya cim ma wannan ta amfani da wannan tambaya:
SANTA COUNT (DUNIYA SupplierID)
FROM samfur;
Wannan tambaya ya dawo da adadin dabi'u masu ban sha'awa da aka samo a cikin sashen SupplierID. A wannan yanayin, amsar ita ce 3, wakiltar 1, 2, da 3.
Ƙididdiga Bayanan Matsala Masu Daidaita
Haɗa aikin COUNT () tare da SABARI sashi don gano adadin bayanan da suka dace da wasu sharuddan. Alal misali, zaton mai kula da sashen yana so ya fahimci matakan jari a cikin sashen. Tambayar da ake biyowa tana gano yawan layuka da ke wakiltar UnitsInStock kasa da raka'a 50:
BABI COUNT (*)
DAGA samfur
BABI BUYUWU BUKATA <50;
A wannan yanayin, tambaya zai dawo da darajar 4, wakiltar Chai, Canza, Syrup Aniseed, da Uncle Bob's Organic Dried Pears.
Ƙungiyar COUNT () za ta iya zama mai matukar muhimmanci ga masu gudanar da bayanai da ke neman taƙaita bayanan da za su dace da bukatun kasuwanci. Tare da ɗan kwarewa kadan, zaka iya amfani da aikin COUNT () don dalilai masu yawa.