Ihe Ị Kwesịrị Ịma Banyere Asụsụ Ajuju Ejiri

The Language Query Language (SQL) bụ setịpụrụ ntụziaka eji emekọrịta na nchekwa data mmekọrịta . N'ezie, SQL bụ asụsụ nke ọtụtụ ọdụ data ghọtara. Mgbe ọ bụla ị na - eji nchekwa data dị otú ahụ eme ihe, software ahụ na - asụgharị iwu gị (ma hà bụ ntinye ma ọ bụ ntinye ndenye) n'ime nkwupụta SQL na nchekwa data maara otú ị ga - esi akọwa ya. SQL nwere isi ihe atọ: asụsụ Diplex Data (DML), Data Definition Language (DDL), na Data Control Language (DCL).

A na-ejikarị SQL eme ihe na Weebụ

Dị ka onye ọrụ nke usoro ngwanrọ nke a na-enweta nchekwa data, ị nwere ike iji SQL, ọbụna ma ọ bụrụ na ị maghị ya. Dịka ọmụmaatụ, ebe nrụọrụ weebụ dị ike nke nchekwa data (dị ka ọtụtụ weebụsaịtị) na-ewebata ntinye ọrụ site na ụdị na clicks na-eji ya edepụta ajụjụ SQL nke na-eweghachite ozi site na nchekwa data achọrọ iji nyefee ibe weebụ ọzọ.

Tụlee ihe atụ nke nchịkọta dị n'ịntanetị na ọrụ ọchụchọ. Ojuju akwukwo a nwere ike ibu akwukwo nke nwere nani igbe ederede nke i tinyere okwu nchicho wee pia igodo ọchụchọ. Mgbe ị pịrị bọtịnụ ahụ, sava weebụ na-eweghachite ihe ndekọ ọ bụla site na data nchekwa data nke nwere okwu ọchụchọ ma jiri nsonaazụ mepụta ibe weebụ kpọmkwem maka arịrịọ gị.

Dịka ọmụmaatụ, ọ bụrụ na ịchọrọ maka ngwaahịa ndị nwere okwu ahụ bụ "Irish," ihe nkesa ahụ nwere ike iji nkwupụta SQL ndị a iji weghachite ngwaahịa ndị metụtara ya:

CHINE * FROM ngwaahịa MERE aha dị ka '% irish%'

N'ịbụ nke a sụgharịrị, iwu a na-eweghachite ihe ndekọ ọ bụla site na tebụl nchekwa data ahụ bụ "ngwaahịa" nke nwere mkpụrụedemede "irish" n'ebe ọ bụla n'ime aha ngwaahịa ahụ.

Asụsụ nchịkwa data

Asụsụ Nhazi Data (DML) nwere mpaghara nke iwu SQL ndị a na-ejikarị eme ihe - ndị na-ejikarị ọdịnaya nke nchekwa data na ụdị ụfọdụ. Iwu DML kachasị na-enye iwu ka eweghachite ozi site na nchekwa data (SELECT), tinye ozi ọhụrụ na nchekwa data (iwu INSERT), gbanwee ozi ugbu a echekwara na nchekwa data (iwu UPDATE), wepu ozi site na nchekwa data Iwu mkpochapu).

Asụsụ nchịkọta data

Asụsụ Data Definition (DDL) nwere iwu ndị a na-ejikarị emekarị. DDL nyere iwu ka ị gbanwee usoro nke nchekwa data, kama nchekwa ọdịnaya. Ihe atụ nke iwu DDL a na-ejikarị eme ihe gụnyere ndị na-eji iji teepu tebụl nchekwa data (CREATE TABLE), gbanwee usoro nke tebụl nchekwa data (ALWA TABLE), ma hichapụ tebụl nchekwa data (DROP TABLE).

Asụsụ nchịkwa data

A na-ejikwa Asụsụ Nchịkwa Data (DCL) jikwaa njikwa onye ọrụ na-abanye na ọdụ data . Ọ nwere iwu abụọ: iwu GỤRỤ, jiri itinye ikikere nchekwa data maka onye ọrụ, na iwu REVOKE, jiri iwepụ ikikere dị. Iwu abụọ ndị a na-etolite isi nke nsụba nchekwa data nchekwa.

Ebube Iwu SQL

Ọ dị mma maka ndị anyị na-abụghị ndị na-emepụta kọmputa, iwu SQL ka e nwere syntax yiri asụsụ Bekee. Ha na-amalitekarị site na nkwupụta iwu na-akọwa ihe ị ga-eme, gbakwunyere amaokwu nke na-akọwa ihe mgbakwunye nke iwu ahụ (dịka tebụl a kapịrị ọnụ n'ime nchekwa data nke iwu ahụ na-emetụta) na n'ikpeazụ, usoro nke edemede ndị na-enye ntụziaka ndị ọzọ.

Mgbe mgbe, naanị ịgụpụta nkwupụta SQL ga-enye gị ezigbo echiche nke ihe iwu ahụ bu n'obi ime. Were oge gụọ ihe atụ a nke nkwupụta SQL:

Kpochapụ ụmụ akwụkwọ MGBE graduation_year = 2014

Ị nwere ike ịmata ihe nkwupụta a ga-eme? Ọ na-enweta tebụl nke onye akwụkwọ ahụ na nchekwa data ma wepụ ihe ndekọ niile maka ụmụ akwụkwọ ndị gụsịrị akwụkwọ n'afọ 2014.

Ịmụta mmemme SQL

Anyi elelere otutu ihe omuma atu di n'isiokwu a, ma SQL bu okwu di ike ma di ike. Maka ihe omimi omimi, lee SQL Fundamentals .