Added ForeignKeys to tables

Author: Cobeine

src/main/java/me/cobeine/sqlava/connection/database/table/ForeignKey.java

@@ -0,0 +1,31 @@
+package me.cobeine.sqlava.connection.database.table;
+
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+/**
+ * @author <a href="https://github.com/Cobeine">Cobeine</a>
+ */
+@RequiredArgsConstructor
+public class ForeignKey {
+    final String foreignKey;
+    String referencedColumn;
+    String referencedTable;
+    OnDelete onDelete;
+
+
+    public static ForeignKey foreignKey(String foreignKey) {
+        return new ForeignKey(foreignKey);
+    }
+
+    public ForeignKey references(String referencedTable, String referencedColumn) {
+        this.referencedTable = referencedTable;
+        this.referencedColumn = referencedColumn;
+        return this;
+    }
+
+    public ForeignKey onDelete(OnDelete onDelete) {
+        this.onDelete = onDelete;
+        return this;
+    }
+}

src/main/java/me/cobeine/sqlava/connection/database/table/OnDelete.java

@@ -0,0 +1,10 @@
+package me.cobeine.sqlava.connection.database.table;
+
+/**
+ * @author <a href="https://github.com/Cobeine">Cobeine</a>
+ */
+
+public enum OnDelete {
+    CASCADE, SET_NULL, RESTRICT, NO_ACTION, SET_DEFAULT, DO_NOTHING
+
+}

src/main/java/me/cobeine/sqlava/connection/database/table/Table.java

@@ -16,16 +16,24 @@ public abstract class Table {
     @Getter private final String name;
     private final List<Column> columns;
     private String primaryKey;
+    private final List<ForeignKey> foreignKeys;
 
     public Table(String name) {
         this.name = name;
         this.columns = new ArrayList<>();
+        this.foreignKeys = new ArrayList<>();
     }
 
     public void addColumn(@NotNull Column column) {
         this.columns.add(column);
     }
 
+    private ForeignKey foreignKey(String key) {
+        ForeignKey entry = new ForeignKey(key);
+        foreignKeys.add(entry);
+        return entry;
+    }
+
     public void addColumns(@NotNull Column... columns) {
         for (Column column : columns) {
             addColumn(column);
@@ -52,6 +60,17 @@ public String toString() {
             builder.deleteCharAt(builder.length() - 1);
             builder.deleteCharAt(builder.length() - 1); //to remove the last ", "
         }
+        if (!foreignKeys.isEmpty()) {
+            for (ForeignKey entry : foreignKeys) {
+                if (entry.referencedColumn != null) {
+                    builder.append(", FOREIGN KEY (`").append(entry.foreignKey).append("`)");
+                    builder.append(" REFERENCES `").append(entry.referencedTable).append("`(`").append(entry.referencedColumn).append("`)");
+                    if (entry.onDelete != null) {
+                        builder.append(" ON DELETE ").append(entry.onDelete.name().replace("_"," "));
+                    }
+                }
+            }
+        }
         builder.append(")");
         return builder.toString();
     }