diff --git a/src/executor/initializer.rs b/src/executor/initializer.rs
index 1620cfe..60d8876 100644
--- a/src/executor/initializer.rs
+++ b/src/executor/initializer.rs
@@ -132,6 +132,7 @@ impl Executor {
         self.check_output_status(output)
     }
 
+    #[allow(dead_code)]
     async fn write_and_check_err(
         &self,
         base_path: PathBuf,
diff --git a/src/lexer/test/select.rs b/src/lexer/test/select.rs
index 51ba2c5..86a083a 100644
--- a/src/lexer/test/select.rs
+++ b/src/lexer/test/select.rs
@@ -188,6 +188,17 @@ pub fn test_operators() {
                 Token::Integer(2),
             ],
         },
+        TestCase {
+            name: "연산자: <=".to_owned(),
+            input: r#"SELECT 1 <= 2"#.to_owned(),
+            want_error: false,
+            expected: vec![
+                Token::Select,
+                Token::Integer(1),
+                Token::Operator(OperatorToken::Lte),
+                Token::Integer(2),
+            ],
+        },
         TestCase {
             name: "연산자: >".to_owned(),
             input: r#"SELECT 1 > 2"#.to_owned(),
@@ -199,6 +210,17 @@ pub fn test_operators() {
                 Token::Integer(2),
             ],
         },
+        TestCase {
+            name: "연산자: >=".to_owned(),
+            input: r#"SELECT 1 >= 2"#.to_owned(),
+            want_error: false,
+            expected: vec![
+                Token::Select,
+                Token::Integer(1),
+                Token::Operator(OperatorToken::Gte),
+                Token::Integer(2),
+            ],
+        },
         TestCase {
             name: "연산자: -".to_owned(),
             input: r#"SELECT 1 - 2"#.to_owned(),
@@ -243,6 +265,17 @@ pub fn test_operators() {
                 Token::Integer(2),
             ],
         },
+        TestCase {
+            name: "연산자: !=".to_owned(),
+            input: r#"SELECT 1 != 2"#.to_owned(),
+            want_error: false,
+            expected: vec![
+                Token::Select,
+                Token::Integer(1),
+                Token::Operator(OperatorToken::Neq),
+                Token::Integer(2),
+            ],
+        },
         TestCase {
             name: "연산자: !".to_owned(),
             input: r#"SELECT ! True"#.to_owned(),
diff --git a/src/lexer/tokenizer.rs b/src/lexer/tokenizer.rs
index a036d4f..42f2a89 100644
--- a/src/lexer/tokenizer.rs
+++ b/src/lexer/tokenizer.rs
@@ -284,10 +284,46 @@ impl Tokenizer {
                 }
                 '+' => Token::Operator(OperatorToken::Plus),
                 '*' => Token::Operator(OperatorToken::Asterisk),
-                '!' => Token::Operator(OperatorToken::Not), // TODO: != 연산자 처리
+                '!' => {
+                    // 다음 문자가 =일 경우 != 연산자로 처리
+
+                    self.read_char();
+
+                    if self.last_char == '=' {
+                        Token::Operator(OperatorToken::Neq)
+                    } else {
+                        self.unread_char();
+
+                        Token::Operator(OperatorToken::Not)
+                    }
+                }
                 '=' => Token::Operator(OperatorToken::Eq),
-                '<' => Token::Operator(OperatorToken::Lt), // TODO: <= 연산자 처리
-                '>' => Token::Operator(OperatorToken::Gt), // TODO: >= 연산자 처리
+                '<' => {
+                    // 다음 문자가 =일 경우 <= 연산자로 처리
+
+                    self.read_char();
+
+                    if self.last_char == '=' {
+                        Token::Operator(OperatorToken::Lte)
+                    } else {
+                        self.unread_char();
+
+                        Token::Operator(OperatorToken::Lt)
+                    }
+                }
+                '>' => {
+                    // 다음 문자가 =일 경우 >= 연산자로 처리
+
+                    self.read_char();
+
+                    if self.last_char == '=' {
+                        Token::Operator(OperatorToken::Gte)
+                    } else {
+                        self.unread_char();
+
+                        Token::Operator(OperatorToken::Gt)
+                    }
+                }
                 _ => {
                     return Err(LexingError::wrap(format!(
                         "unexpected operator: {:?}",