Utilize null safe equals

src/de/steamwar/sql/internal/SelectStatement.java

@@ -31,7 +31,7 @@ public class SelectStatement<T> extends Statement {
     private final Table<T> table;
 
     SelectStatement(Table<T> table, String... kfields) {
-        this(table, "SELECT " + Arrays.stream(table.fields).map(f -> f.identifier).collect(Collectors.joining(", ")) + " FROM " + table.name + " WHERE " + Arrays.stream(kfields).map(f -> f + " = ?").collect(Collectors.joining(" AND ")));
+        this(table, "SELECT " + Arrays.stream(table.fields).map(f -> f.identifier).collect(Collectors.joining(", ")) + " FROM " + table.name + " WHERE " + Arrays.stream(kfields).map(f -> f + Statement.NULL_SAFE_EQUALS + "?").collect(Collectors.joining(" AND ")));
     }
 
     public SelectStatement(Table<T> table, String sql) {

src/de/steamwar/sql/internal/Statement.java

@@ -41,6 +41,7 @@ public class Statement implements AutoCloseable {
     static final Consumer<Table<?>> schemaCreator;
     static final String ON_DUPLICATE_KEY;
     static final UnaryOperator<String> upsertWrapper;
+    public static final String NULL_SAFE_EQUALS;
 
     private static final boolean MYSQL_MODE;
     private static final boolean PRODUCTION_DATABASE;
@@ -73,6 +74,7 @@ public class Statement implements AutoCloseable {
             schemaCreator = table -> {};
             ON_DUPLICATE_KEY = " ON DUPLICATE KEY UPDATE ";
             upsertWrapper = f -> f + " = VALUES(" + f + ")";
+            NULL_SAFE_EQUALS = " <=> ";
         } else {
             Connection connection;
 
@@ -89,6 +91,7 @@ public class Statement implements AutoCloseable {
             schemaCreator = Table::ensureExistanceInSqlite;
             ON_DUPLICATE_KEY = " ON CONFLICT DO UPDATE SET ";
             upsertWrapper = f -> f + " = " + f;
+            NULL_SAFE_EQUALS = " IS ";
         }
     }
 

src/de/steamwar/sql/internal/Table.java

@@ -75,7 +75,7 @@ public class Table<T> {
     }
 
     public Statement updateFields(String[] fields, String... kfields) {
-        return new Statement("UPDATE " + name + " SET " + Arrays.stream(fields).map(f -> f + " = ?").collect(Collectors.joining(", ")) + " WHERE " + Arrays.stream(kfields).map(f -> f + " = ?").collect(Collectors.joining(" AND ")));
+        return new Statement("UPDATE " + name + " SET " + Arrays.stream(fields).map(f -> f + " = ?").collect(Collectors.joining(", ")) + " WHERE " + Arrays.stream(kfields).map(f -> f + Statement.NULL_SAFE_EQUALS + "?").collect(Collectors.joining(" AND ")));
     }
 
     public Statement insert(String name) {
@@ -100,7 +100,7 @@ public class Table<T> {
     }
 
     public Statement deleteFields(String... kfields) {
-        return new Statement("DELETE FROM " + name + " WHERE " + Arrays.stream(kfields).map(f -> f + " = ?").collect(Collectors.joining(" AND ")));
+        return new Statement("DELETE FROM " + name + " WHERE " + Arrays.stream(kfields).map(f -> f + Statement.NULL_SAFE_EQUALS + "?").collect(Collectors.joining(" AND ")));
     }
 
     void ensureExistanceInSqlite() {