diff --git a/spring-jdbc-1/initial/src/main/java/cholog/QueryingDAO.java b/spring-jdbc-1/initial/src/main/java/cholog/QueryingDAO.java
index 6f299728..d28e1e0c 100644
--- a/spring-jdbc-1/initial/src/main/java/cholog/QueryingDAO.java
+++ b/spring-jdbc-1/initial/src/main/java/cholog/QueryingDAO.java
@@ -31,7 +31,7 @@ public QueryingDAO(JdbcTemplate jdbcTemplate) {
      */
     public int count() {
         //TODO : customers 디비에 포함되어있는 row가 몇개인지 확인하는 기능 구현
-        return 0;
+        return jdbcTemplate.queryForObject("select count(*) from customers", Integer.class);
     }
 
     /**
@@ -39,33 +39,57 @@ public int count() {
      */
     public String getLastName(Long id) {
         //TODO : 주어진 Id에 해당하는 customers의 lastName을 반환
-        return null;
+        return jdbcTemplate.queryForObject("select last_name from customers where id = ?", String.class, id);
     }
 
     /**
      * public <T> T queryForObject(String sql, RowMapper<T> rowMapper, @Nullable Object... args)
      */
     public Customer findCustomerById(Long id) {
-        String sql = "select id, first_name, last_name from customers where id = ?";
         //TODO : 주어진 Id에 해당하는 customer를 객체로 반환
-        return null;
+        return jdbcTemplate.queryForObject(
+                "select id, first_name, last_name from customers where id = ?",
+                (resultSet, rowNum) -> {
+                    Customer customer = new Customer(
+                            resultSet.getLong("id"),
+                            resultSet.getString("first_name"),
+                            resultSet.getString("last_name")
+                    );
+                    return customer;
+                }, id);
     }
 
     /**
      * public <T> List<T> query(String sql, RowMapper<T> rowMapper)
      */
     public List<Customer> findAllCustomers() {
-        String sql = "select id, first_name, last_name from customers";
         //TODO : 저장된 모든 Customers를 list형태로 반환
-        return null;
+        return jdbcTemplate.query(
+                "select id, first_name, last_name from customers",
+                (resultSet, rowNum) -> {
+                    Customer customer = new Customer(
+                            resultSet.getLong("id"),
+                            resultSet.getString("first_name"),
+                            resultSet.getString("last_name")
+                    );
+                    return customer;
+                });
     }
 
     /**
      * public <T> List<T> query(String sql, RowMapper<T> rowMapper, @Nullable Object... args)
      */
     public List<Customer> findCustomerByFirstName(String firstName) {
-        String sql = "select id, first_name, last_name from customers where first_name = ?";
         //TODO : firstName을 기준으로 customer를 list형태로 반환
-        return null;
+        return jdbcTemplate.query(
+                "select id, first_name, last_name from customers where first_name = ?",
+                (resultSet, rowNum) -> {
+                    Customer customer = new Customer(
+                            resultSet.getLong("id"),
+                            resultSet.getString("first_name"),
+                            resultSet.getString("last_name")
+                    );
+                    return customer;
+                }, firstName);
     }
 }
diff --git a/spring-jdbc-1/initial/src/main/java/cholog/UpdatingDAO.java b/spring-jdbc-1/initial/src/main/java/cholog/UpdatingDAO.java
index e53c21ef..b5cc781d 100644
--- a/spring-jdbc-1/initial/src/main/java/cholog/UpdatingDAO.java
+++ b/spring-jdbc-1/initial/src/main/java/cholog/UpdatingDAO.java
@@ -33,26 +33,32 @@ public UpdatingDAO(JdbcTemplate jdbcTemplate) {
      */
     public void insert(Customer customer) {
         //todo: customer를 디비에 저장하기
+        jdbcTemplate.update("insert into customers (first_name, last_name) values (?, ?)",
+                customer.getFirstName(), customer.getLastName());
     }
     /**
      * public int update(String sql, @Nullable Object... args)
      */
     public int delete(Long id) {
         //todo: id에 해당하는 customer를 지우고, 해당 쿼리에 영향받는 row 수반환하기
-        return 0;
+        return jdbcTemplate.update("delete from customers where id = ?", Long.valueOf(id));
     }
 
     /**
      * public int update(final PreparedStatementCreator psc, final KeyHolder generatedKeyHolder)
      */
     public Long insertWithKeyHolder(Customer customer) {
-        String sql = "insert into customers (first_name, last_name) values (?, ?)";
         KeyHolder keyHolder = new GeneratedKeyHolder();
-
-        //todo : keyHolder에 대해 학습하고, Customer를 저장후 저장된 Customer의 id를 반환하기
+        jdbcTemplate.update(connection -> {
+            PreparedStatement ps = connection.prepareStatement(
+                    "insert into customers (first_name, last_name) values (?, ?)",
+                    new String[]{"id"});
+            ps.setString(1, customer.getFirstName());
+            ps.setString(2, customer.getLastName());
+            return ps;
+        }, keyHolder);
 
         Long id = keyHolder.getKey().longValue();
-
-        return keyHolder.getKey().longValue();
+        return id;
     }
 }