try string converter

kbazaar/src/main/java/com/kampus/kbazaar/promotion/Promotion.java

@@ -3,7 +3,8 @@
 import jakarta.persistence.*;
 import java.math.BigDecimal;
 import java.time.LocalDateTime;
-import java.util.List;
+import java.util.*;
+
 import lombok.AllArgsConstructor;
 import lombok.Data;
 import lombok.NoArgsConstructor;
@@ -45,12 +46,9 @@ public class Promotion {
     @Column(name = "applicable_to", nullable = false)
     private String applicableTo;
 
-    @ElementCollection
-    @CollectionTable(
-            name = "promotion_product_skus",
-            joinColumns = @JoinColumn(name = "promotion_id"))
-    @Column(name = "product_sku")
-    private List<String> productSkus;
+    @Convert(converter = StringListConverter.class)
+    @Column(name = "product_skus")
+    private List<String> productSkus;;
 
     @Column(name = "min_quantity")
     private Integer minQuantity;

kbazaar/src/main/java/com/kampus/kbazaar/promotion/PromotionResponse.java

@@ -3,6 +3,7 @@
 import java.math.BigDecimal;
 import java.time.LocalDateTime;
 import java.util.List;
+import java.util.Set;
 
 public record PromotionResponse(
         Long promotionId,

kbazaar/src/main/java/com/kampus/kbazaar/promotion/StringListConverter.java

@@ -0,0 +1,29 @@
+package com.kampus.kbazaar.promotion;
+
+import jakarta.persistence.AttributeConverter;
+import jakarta.persistence.Converter;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static java.util.Collections.emptyList;
+
+@Converter
+public class StringListConverter implements AttributeConverter<List<String>, String> {
+    private static final String SPLIT_CHAR = ",";
+
+    @Override
+    public String convertToDatabaseColumn(List<String> values) {
+        return values != null ? String.format("{%s}", String.join(SPLIT_CHAR, values)) : "";
+    }
+
+    @Override
+    public List<String> convertToEntityAttribute(String value) {
+        if (value == null) {
+            return emptyList();
+        }
+
+        String vs = value.replace("{", "").replace("}", "");
+        return Arrays.asList(vs.split(SPLIT_CHAR));
+    }
+}

kbazaar/src/main/resources/sql/schema/product.sql

@@ -3,7 +3,5 @@ CREATE TABLE IF NOT EXISTS product (
 	name VARCHAR(255) NOT NULL,
 	price DECIMAL(10, 2) NOT NULL,
 	quantity INT NOT NULL,
-	sku VARCHAR(255) NOT NULL UNIQUE,
-	created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-	updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+	sku VARCHAR(255) NOT NULL UNIQUE
 );