📁 WHERE

💡 WHERE절은 특정 조건에 맞는 레코드만을 선택하는데 사용되며 다양한 방법으로 조건을 설정 가능

🔖 비교 연산자 활용

➡️ 같음(=) 연산자:

SELECT menu_name, menu_price, orderable_status
  FROM tbl_menu
 WHERE orderable_status = 'Y';

SELECT menu_name, menu_price, orderable_status
  FROM tbl_menu
 WHERE menu_price = 13000;

➡️ 같지 않음(!=, <>) 연산자:

SELECT menu_code, menu_name, orderable_status
  FROM tbl_menu
--  WHERE orderable_status <> 'Y';
 WHERE orderable_status != 'Y';

➡️ 대소 비교 연산자:

SELECT menu_code, menu_name, menu_price
  FROM tbl_menu
 WHERE menu_price > 20000;

SELECT menu_code, menu_name, menu_price
  FROM tbl_menu
 WHERE menu_price <= 20000;

---

🔖 AND 연산자 활용

➡️ AND 연산자:

SELECT menu_name, menu_price, category_code, orderable_status
  FROM tbl_menu
 WHERE orderable_status = 'Y'
   AND category_code = 10;

SELECT menu_code, menu_name, menu_price, category_code, orderable_status
  FROM tbl_menu
 WHERE menu_price > 5000
   AND category_code = 10;

---

🔖 OR 연산자 활용

➡️ OR 연산자:

SELECT menu_name, menu_price, category_code, orderable_status
  FROM tbl_menu
 WHERE orderable_status = 'Y'
    OR category_code = 10
 ORDER BY category_code;

SELECT menu_code, menu_name, menu_price, category_code, orderable_status
  FROM tbl_menu
 WHERE menu_price > 5000
    OR category_code = 10;

➡️ AND와 OR의 우선순위:

SELECT menu_code, menu_name, menu_price, category_code, orderable_status
  FROM tbl_menu
 WHERE category_code = 4
    OR menu_price = 9000
   AND menu_code > 10;

---

🔖 BETWEEN 연산자 활용

➡️ BETWEEN 연산자:

SELECT menu_name, menu_price, category_code
  FROM tbl_menu
 WHERE menu_price BETWEEN 10000 AND 25000
 ORDER BY menu_price;

➡️NOT BETWEEN 연산자:

SELECT menu_name, menu_price, category_code
  FROM tbl_menu
 WHERE menu_price NOT BETWEEN 10000 AND 25000
 ORDER BY menu_price;

---

🔖 LIKE 연산자 활용

➡️LIKE 연산자:

SELECT menu_name, menu_price
  FROM tbl_menu
 WHERE menu_name LIKE '%마늘%'
 ORDER BY menu_name;

SELECT menu_code, menu_name, menu_price, category_code, orderable_status
  FROM tbl_menu
 WHERE menu_price > 5000
   AND category_code = 10
   AND menu_name LIKE '%갈치%';

➡️ NOT LIKE 연산자:

SELECT menu_name, menu_price
  FROM tbl_menu
 WHERE menu_name NOT LIKE '%마늘%'
 ORDER BY menu_name;

---

🔖 IN 연산자 활용

➡️ IN 연산자:

SELECT menu_name, category_code
  FROM tbl_menu
 WHERE category_code IN (4, 5, 6)
 ORDER BY category_code;

➡️ NOT IN 연산자:

SELECT menu_name, category_code
  FROM tbl_menu
 WHERE category_code NOT IN (4, 5, 6)
 ORDER BY category_code;

---

🔖 IS NULL 연산자 활용

➡️ IS NULL 연산자:

SELECT category_code, category_name, ref_category_code
  FROM tbl_category
 WHERE ref_category_code IS NULL;

➡️ IS NOT NULL 연산자:

SELECT category_code, category_name, ref_category_code
  FROM tbl_category
 WHERE ref_category_code IS NOT NULL;