feat: update solutions to lc problems: No.0183,0584,0595,1757

- No.0183.Customers Who Never Order
- No.0584.Find Customer Referee
- No.0595.Big Countries
- No.1757.Recyclable and Low Fat Products

Author: YangFong

solution/0100-0199/0183.Customers Who Never Order/README.md

@@ -57,19 +57,22 @@
 ### **SQL**
 
 ```sql
-select Name as Customers from Customers
-    where id not in (select CustomerId from Orders)
+select Name as Customers
+from Customers
+where id not in (
+        select CustomerId
+        from Orders
+    );
 ```
 
 ```sql
-# Write your MySQL query statement below
 SELECT
-	c.Name AS Customers
+    c.Name AS Customers
 FROM
-	customers AS c
-	LEFT JOIN orders AS o ON c.Id  = o.CustomerId
+    customers AS c
+    LEFT JOIN orders AS o ON c.Id  = o.CustomerId
 WHERE
-	o.CustomerId IS NULL
+    o.CustomerId IS NULL;
 ```
 
 <!-- tabs:end -->

solution/0100-0199/0183.Customers Who Never Order/README_EN.md

@@ -78,19 +78,22 @@ Orders table:
 ### **SQL**
 
 ```sql
-select Name as Customers from Customers
-    where id not in (select CustomerId from Orders)
+select Name as Customers
+from Customers
+where id not in (
+        select CustomerId
+        from Orders
+    );
 ```
 
 ```sql
-# Write your MySQL query statement below
 SELECT
-	c.Name AS Customers
+    c.Name AS Customers
 FROM
-	customers AS c
-	LEFT JOIN orders AS o ON c.Id  = o.CustomerId
+    customers AS c
+    LEFT JOIN orders AS o ON c.Id  = o.CustomerId
 WHERE
-	o.CustomerId IS NULL
+    o.CustomerId IS NULL;
 ```
 
 <!-- tabs:end -->

solution/0100-0199/0183.Customers Who Never Order/Solution.sql

@@ -1,2 +1,6 @@
-select Name as Customers from Customers
-    where id not in (select CustomerId from Orders)
+select Name as Customers
+from Customers
+where id not in (
+        select CustomerId
+        from Orders
+    );

solution/0500-0599/0584.Find Customer Referee/README.md

@@ -53,4 +53,15 @@ WHERE
     referee_id != 2 OR referee_id IS NULL;
 ```
 
+MySQL 可使用 `IFNULL()`：
+
+```sql
+SELECT
+    name
+FROM
+    customer
+WHERE
+    IFNULL(referee_id, 0) != 2;
+```
+
 <!-- tabs:end -->

solution/0500-0599/0584.Find Customer Referee/README_EN.md

@@ -68,4 +68,16 @@ WHERE
     referee_id != 2 OR referee_id IS NULL;
 ```
 
+MySQL can use `IFNULL()`:
+
+```sql
+SELECT
+    name
+FROM
+    customer
+WHERE
+    IFNULL(referee_id, 0) != 2;
+```
+
+
 <!-- tabs:end -->

solution/0500-0599/0595.Big Countries/README.md

@@ -76,13 +76,13 @@ World 表：
 
 ### **SQL**
 
-```
+```sql
 SELECT name,
-         population,
-         area
-FROM World
-WHERE area>3000000
-        OR population>25000000
+        population,
+        area
+FROM world
+WHERE area > 3000000
+        OR population > 25000000;
 ```
 
 <!-- tabs:end -->

solution/0500-0599/0595.Big Countries/README_EN.md

@@ -65,13 +65,13 @@ World table:
 
 ### **SQL**
 
-```
+```sql
 SELECT name,
-         population,
-         area
-FROM World
-WHERE area>3000000
-        OR population>25000000
+        population,
+        area
+FROM world
+WHERE area > 3000000
+        OR population > 25000000;
 ```
 
 <!-- tabs:end -->

solution/0500-0599/0595.Big Countries/Solution.sql

@@ -1,6 +1,6 @@
 SELECT name,
-         population,
-         area
-FROM World
-WHERE area>3000000
-        OR population>25000000
+        population,
+        area
+FROM world
+WHERE area > 3000000
+        OR population > 25000000;

solution/1700-1799/1757.Recyclable and Low Fat Products/README.md

@@ -58,14 +58,13 @@ Result 表：
 ### **SQL**
 
 ```sql
-# Write your MySQL query statement below
 SELECT
     product_id
 FROM
     Products
 WHERE
     low_fats = 'Y'
-AND recyclable = 'Y';
+    AND recyclable = 'Y';
 ```
 
 <!-- tabs:end -->

solution/1700-1799/1757.Recyclable and Low Fat Products/README_EN.md

@@ -58,14 +58,13 @@ Products table:
 ### **SQL**
 
 ```sql
-# Write your MySQL query statement below
 SELECT
     product_id
 FROM
     Products
 WHERE
     low_fats = 'Y'
-AND recyclable = 'Y';
+    AND recyclable = 'Y';
 ```
 
 <!-- tabs:end -->

solution/1700-1799/1757.Recyclable and Low Fat Products/Solution.sql

@@ -1,8 +1,7 @@
-# Write your MySQL query statement below
 SELECT
     product_id
 FROM
     Products
 WHERE
     low_fats = 'Y'
-AND recyclable = 'Y';
+    AND recyclable = 'Y';