여러분이 사용하고 계신 브라우저는 HTML5를 지원하지 않기 때문에 몇몇 요소가 제대로 보이도록 JScript를 사용하고 있습니다. 하지만 여러분의 브라우저 설정에서 스크립트 기능이 꺼져있으므로, 현재 페이지를 제대로 확인하시려면 스크립트 기능을 켜주셔야 합니다. SQL - LEFT JOIN 키워드
SQL – LEFT JOIN 키워드
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LEFT JOIN

LEFT JOIN 키워드는 왼쪽 테이블(table1)의 모든 레코드와 오른쪽 테이블(table2)의 일치하는 레코드를 반환한다.
일치하는 레코드가 없는 경우 결과는 오른쪽에서 0개의 레코드가 생성된다.

⭐ 일부 SQL에서는 LEFT JOIN을 OUTER JOIN 이라고도 한다.

LEFT JOIN

구문

SELECT column_name(s)
FROM table1
LEFT JOIN table2
ON table1.column_name = table2.column_name;

데이터베이스 예시

고객 테이블

CustomerID CustomerName ContactName Address City PostalCode Country
1

Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany
2 Ana Trujillo Emparedados y helados Ana Trujillo Avda. de la Constitución 2222 México D.F. 05021 Mexico
3 Antonio Moreno Taquería Antonio Moreno Mataderos 2312 México D.F. 05023 Mexico

주문 테이블

OrderID CustomerID EmployeeID OrderDate ShipperID
10308 2 7 1996-09-18 3
10309 37 3 1996-09-19 1
10310 77 8 1996-09-20 2

모든 고객과 고객이 가질 수 있는 주문을 선택

⭐ LEFT JOIN 키워드는 오른쪽 테이블(주문)에 일치하는 항목이 없는 경우에도 왼쪽 테이블(고객)의 모든 레코드를 반환한다.

SELECT Customers.CustomerName, Orders.OrderID
FROM Customers
LEFT JOIN Orders ON Customers.CustomerID = Orders.CustomerID
ORDER BY Customers.CustomerName;
기본 예시
CustomerName OrderID
Alfreds Futterkiste null
Ana Trujillo Emparedados y helados 10308
Antonio Moreno Taquería 10365
Around the Horn 10355
Around the Horn 10383
B’s Beverages 10289
Berglunds snabbköp 10278
Berglunds snabbköp 10280
Berglunds snabbköp 10384
Blauer See Delikatessen null
Blondel père et fils 10265
Blondel père et fils 10297
Blondel père et fils 10360
Blondel père et fils 10436
Bon app’ 10331
Bon app’ 10340
Bon app’ 10362
Bottom-Dollar Marketse 10389
Bottom-Dollar Marketse 10410
Bottom-Dollar Marketse 10411
Bottom-Dollar Marketse 10431
Bólido Comidas preparadas 10326
Cactus Comidas para llevar null
Centro comercial Moctezuma 10259
Chop-suey Chinese 10254
Chop-suey Chinese 10370
Comércio Mineiro 10290
Consolidated Holdings 10435
Die Wandernde Kuh 10301
Die Wandernde Kuh 10312
Die Wandernde Kuh 10348
Die Wandernde Kuh 10356
Drachenblut Delikatessend 10363
Drachenblut Delikatessend 10391
Du monde entier 10311
Eastern Connection 10364
Eastern Connection 10400
Ernst Handel 10258
Ernst Handel 10263
Ernst Handel 10351
Ernst Handel 10368
Ernst Handel 10382
Ernst Handel 10390
Ernst Handel 10402
Ernst Handel 10403
Ernst Handel 10430
Ernst Handel 10442
FISSA Fabrica Inter. Salchichas S.A. null
Familia Arquibaldo 10347
Familia Arquibaldo 10386
Familia Arquibaldo 10414
Folies gourmandes 10408
Folk och fä HB 10264
Folk och fä HB 10327
Folk och fä HB 10378
Folk och fä HB 10434
France restauration null
Franchi S.p.A. 10422
Frankenversand 10267
Frankenversand 10337
Frankenversand 10342
Frankenversand 10396
Furia Bacalhau e Frutos do Mar 10328
Furia Bacalhau e Frutos do Mar 10352
GROSELLA-Restaurante 10268
Galería del gastrónomo 10366
Galería del gastrónomo 10426
Godos Cocina Típica 10303
Gourmet Lanchonetes 10423
Great Lakes Food Market null
HILARIÓN-Abastos 10257
HILARIÓN-Abastos 10395
Hanari Carnes 10250
Hanari Carnes 10253
Hungry Coyote Import Store 10375
Hungry Coyote Import Store 10394
Hungry Coyote Import Store 10415
Hungry Owl All-Night Grocers 10298
Hungry Owl All-Night Grocers 10309
Hungry Owl All-Night Grocers 10335
Hungry Owl All-Night Grocers 10373
Hungry Owl All-Night Grocers 10380
Hungry Owl All-Night Grocers 10429
Island Trading 10315
Island Trading 10318
Island Trading 10321
Königlich Essen 10323
Königlich Essen 10325
LILA-Supermercado 10283
LILA-Supermercado 10296
LILA-Supermercado 10330
LILA-Supermercado 10357
LILA-Supermercado 10381
LINO-Delicateses 10405
La corne d’abondance null
La maison d’Asie 10350
La maison d’Asie 10358
La maison d’Asie 10371
La maison d’Asie 10413
La maison d’Asie 10425
Laughing Bacchus Wine Cellars null
Lazy K Kountry Store null
Lehmanns Marktstand 10279
Lehmanns Marktstand 10284
Lehmanns Marktstand 10343
Let’s Stop N Shop null
Lonesome Pine Restaurant 10307
Lonesome Pine Restaurant 10317
Magazzini Alimentari Riuniti 10275
Magazzini Alimentari Riuniti 10300
Magazzini Alimentari Riuniti 10404
Maison Dewey null
Morgenstern Gesundkost 10277
Mère Paillarde 10332
Mère Paillarde 10339
Mère Paillarde 10376
Mère Paillarde 10424
Mère Paillarde 10439
North/South null
Océano Atlántico Ltda. 10409
Old World Delicatessen 10260
Old World Delicatessen 10305
Old World Delicatessen 10338
Old World Delicatessen 10441
Ottilies Käseladen 10407
Paris spécialités null
Pericles Comidas clásicas 10322
Pericles Comidas clásicas 10354
Piccolo und mehr 10353
Piccolo und mehr 10392
Piccolo und mehr 10427
Princesa Isabel Vinhoss 10336
Princesa Isabel Vinhoss 10397
Princesa Isabel Vinhoss 10433
QUICK-Stop 10273
QUICK-Stop 10285
QUICK-Stop 10286
QUICK-Stop 10313
QUICK-Stop 10345
QUICK-Stop 10361
QUICK-Stop 10418
Que Delícia 10261
Que Delícia 10291
Que Delícia 10379
Que Delícia 10421
Queen Cozinha 10372
Queen Cozinha 10406
Rancho grande null
Rattlesnake Canyon Grocery 10262
Rattlesnake Canyon Grocery 10272
Rattlesnake Canyon Grocery 10294
Rattlesnake Canyon Grocery 10314
Rattlesnake Canyon Grocery 10316
Rattlesnake Canyon Grocery 10346
Rattlesnake Canyon Grocery 10401
Reggiani Caseifici 10288
Reggiani Caseifici 10428
Reggiani Caseifici 10443
Ricardo Adocicados 10287
Ricardo Adocicados 10299
Richter Supermarkt 10255
Richter Supermarkt 10419
Romero y tomillo 10281
Romero y tomillo 10282
Romero y tomillo 10306
Santé Gourmet 10387
Save-a-lot Markets 10324
Save-a-lot Markets 10393
Save-a-lot Markets 10398
Save-a-lot Markets 10440
Seven Seas Imports 10359
Seven Seas Imports 10377
Seven Seas Imports 10388
Simons bistro 10341
Simons bistro 10417
Split Rail Beer & Ale 10271
Split Rail Beer & Ale 10329
Split Rail Beer & Ale 10349
Split Rail Beer & Ale 10369
Split Rail Beer & Ale 10385
Split Rail Beer & Ale 10432
Spécialités du monde null
Suprêmes délices 10252
Suprêmes délices 10302
The Big Cheese 10310
The Cracker Box null
Toms Spezialitäten 10438
Tortuga Restaurante 10276
Tortuga Restaurante 10293
Tortuga Restaurante 10304
Tortuga Restaurante 10319
Tradição Hipermercados 10249
Tradição Hipermercados 10292
Trail’s Head Gourmet Provisioners null
Vaffeljernet 10367
Vaffeljernet 10399
Victuailles en stock 10251
Victuailles en stock 10334
Vins et alcools Chevalier 10274
Vins et alcools Chevalier 10295
Wartian Herkku 10266
Wartian Herkku 10270
Wartian Herkku 10320
Wartian Herkku 10333
Wartian Herkku 10412
Wartian Herkku 10416
Wartian Herkku 10437
Wellington Importadora 10256
Wellington Importadora 10420
White Clover Markets 10269
White Clover Markets 10344
Wilman Kala 10248
Wolski 10374
참고
Mingg`s Diary
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