?قȂ?e?[?u?????m??????????uJOIN?v???FSQL???H?u???i4?j

?e?[?u?????m??????????ɂ́H

?@????́ASQL???ł̌????̎d???iJOIN?j????????܂??B?O??܂łɐ????????uSELECT?v???́A?uFROM?v???1?‚̃e?[?u???݂̂??w?肷??V???v???ȗ?ł????B????g?p????uJOIN?v???g?p????ƁA?????̃e?[?u??????֘A????f?[?^?𓯎??ɕ\???????邱?Ƃ??ł??܂??B

?@?܂??́A?O??Ɠ??l?uOrder Details?v??\?????Ă݂܂??傤?B

SELECT * FROM "Order Details"

???1?@OrderDetails?e?[?u???̓??e??\?????Ă݂??Ƃ???i??ʂ??N???b?N????Ɗg??\?????܂??j

?@????g?p????uOrder Details?v?e?[?u???̓??e???\??????܂??B???̃e?[?u???́A???钍???iOrderID?j?ɑ΂??āA?ǂ̐??i?iProductID?j??P????????ŁiUnitPrice?j?A?????iQuantity?j?󒍂????????L?^???Ă??܂??B?????ŁA?\?????ꂽ?f?[?^??????ƕ?????Ǝv???܂????A???i?Ɋւ??ẮA2????ProductID???\??????邾???ŁA?ǂ̂悤?Ȑ??i?Ȃ̂??́A???́uOrder Details?v?e?[?u???̓??e?????ł͕?????܂???B

?@???i?Ɋւ?????́A?uProducts?v?e?[?u???ɋL?^????Ă??܂??B?\???????Ă݂܂??傤?B

SELECT ProductID, ProductName, QuantityPerUnit
FROM Products

???2?@????ǂ́AProducts?e?[?u???̓??e??\?????Ă݂??i??ʂ??N???b?N????Ɗg??\?????܂??j

?@?uProducts?v?e?[?u???ɂ́AProductID?̂ق??A???i???iProductName?j?A?P???iUnitPrice?j?Ƃ???????񂪊i?[????Ă??܂??B??L?́uOrder Details?v?e?[?u???̍ŏ??̍s?ɕ\??????Ă???ProductID??11?̐??i?́AQueso Cabrales?Ƃ??????̂ŁA?P????21?h???ł??邱?Ƃ??uProducts?v?e?[?u?????番????܂??ˁB

?@?ł́A?uOrder Details?v??\?????????Ƃ???ProductID???AProductName?ɂ???ɂ͂ǂ???????悢?ł??傤???H

?????ŁA?uJOIN?v?̓o??ł??B

?@?܂??́A??3?????s???Ă݂܂??傤?B

SELECT OrderID, Prd.ProductID, ProductName, Prd.UnitPrice, Quantity, Discount 
FROM "Order Details" Ord 
INNER JOIN Products Prd ON Ord.ProductID=Prd.ProductID

???3?@2?‚̃e?[?u????JOIN???????ʁBProducts?e?[?u?????g????Order Details?e?[?u???̕\?????ʂ?ProductName?𔽉f???邱?Ƃ??ł????i??ʂ??N???b?N????Ɗg??\?????܂??j

?@?????ԁA???G??SQL?ɂȂ?܂????ˁBJOIN???̂??̂????????O?ɁA1??1????ǂ??Đ??????܂??傤?B

?uSELECT?v??ł̗?̎w??

?@???܂܂ł̗?Ɠ??l?ȗ?̎w??ł????AProductID??UnitPrice?̑O?ɂ́A?uPrd.?v?Ƃ????lj??̎w?肪????Ă??܂??B????́AProductID?Ƃ??????O?̗񂪁A?uOrder Details?v?e?[?u???ƁuProducts?v?e?[?u???̗????ɑ??݂??邽?߁A?ǂ???̃e?[?u????ProductID?????w?肷?邽?߂̃e?[?u?????ł??B?e?[?u?????????ł͂Ȃ??A?f?[?^?x?[?X?????w?肷?邱?Ƃ??”\?ł??B?f?[?^?x?[?X???̓e?[?u?????̂???ɑO?ɁA?u.?v?i?s???I?h?j?ŋ?؂??Ďw?肵?܂??B

?ƋL?q???邱?ƂŁA????̃e?[?u???̓???̗???w?肷?邱?Ƃ??ł??܂??B??3?ł́A?f?[?^?x?[?X????e?[?u???????w?肵?Ă??Ȃ??񂪂???܂????A?????񂪑ΏۂƂȂ?Ȃ?????A?ȗ????邱?Ƃ??”\?ł??B???܂܂ł̗?͂??ׂĂ????ł????ˁB

?@?ł́A?uPrd?v?Ƃ????e?[?u???͂???̂ł??傤???H Northwind?f?[?^?x?[?X?̒??ɂ?Prd?Ƃ????e?[?u???͂???܂???B????????ɐ??????܂??B

?e?[?u???̕ʖ????w?肷??

?@??3?̂悤?ɁA?????̃e?[?u????????SELECT???ł̓e?[?u???????w?肷??@??????Ȃ?܂??B?ǂ݂₷?????m?ۂ??邽?߂ɁA?e?[?u?????̕ʖ????w?肷?邱?Ƃ??”\?ł??i?e?[?u?????̕ʖ????w?肷?邱?Ƃ??ł??闝?R?ɂ́A?ق??ɂ???1?‘傫?ȗ??R??????܂????A????͕ʂ̉?Ő??????܂??j?B

SELECT OrderID, Prd.ProductID, ProductName, Prd.UnitPrice, Quantity, Discount 
FROM "Order Details" Ord 
INNER JOIN Products Prd ON Ord.ProductID=Prd.ProductID

?@??3?ł́AFROM??́u"Order Details" Ord?v?̕????ƁAINNER JOIN?߂́uProducts Prd?v?̕??????ʖ??̎w????ł??B???̗?ł́A"Order Details"?e?[?u???́A?uOrd?v?Ƃ????ʖ????w?肵?Ă??܂??̂ŁA????SQL???̒??ł̓e?[?u???????L?q???????Ord?ƋL?q????΁A?????"Order Details"???L?q?????̂Ɠ????Ӗ??ɂȂ?܂??B??3?ł́AProducts?e?[?u???ɑ΂??āA?uPrd?v?Ƃ????ʖ????w?肳??Ă??܂??B

?@?ł͎??ɁA?{???JOIN?ł??B

INNER JOIN??

?@?uOrder Details?v?e?[?u???ƁuProducts?v?e?[?u???????ѕt???Ă???̂́AFROM??̒???INNER JOIN?߂ł??BFROM??ŋL?q?????e?[?u?????̌??INNER JOIN?߂??L?q????ƁAINNER JOIN?߂ɋL?q???ꂽ?e?[?u???ƌ?????????܂??BINNER JOIN?߂̎??ɑ???ON?߂́A?????̍ۂ̏????w??ł??B??3?̏ꍇ?ɂ́A?uOrderDetails?v?e?[?u????ProductID?ƁuProducts?v?e?[?u????ProductID?????????R?[?h???m???A2?‚̃e?[?u???ԂŌ??ѕt?????܂??B

?@??3?ł́A?uOrder Details?v?e?[?u????1?s?ڂ?ProductID??11?ł??̂ŁA?uProducts?v?e?[?u????ProductID??11?̍s?ƌ??ѕt?????܂??BProductID??11?̍s??ProductName?́uQueso Cabrales?v?ł??̂ŁA???ꂪ??3??1?s?ڂ̌??ʂƂ??ĕ\??????Ă???킯?ł??B???́A?uOrder Details?v?e?[?u????2?s?ڂ?ProductID??42?ł??̂ŁA?uProducts?v?e?[?u????ProductID??42?̍s?ƌ??ѕt?????܂??B???̂悤?ɁA?uOrder Details?v?e?[?u???̂??ׂĂ̍s?ɑ΂??āA?Y??????uProducts?v?e?[?u???̍s?????ѕt??????A?Ƃ????d?g?݂ł??B