feat: 添加取相反数的构建。

mybatis-flex-core/src/main/java/com/mybatisflex/core/query/NegativeQueryColumn.java

@@ -0,0 +1,40 @@
+package com.mybatisflex.core.query;
+
+import com.mybatisflex.core.FlexConsts;
+import com.mybatisflex.core.dialect.IDialect;
+
+import java.util.List;
+
+/**
+ * 取相反数（{@code -column}）。
+ *
+ * @author 王帅
+ * @since 2023-11-09
+ */
+public class NegativeQueryColumn extends QueryColumn implements HasParamsColumn {
+
+    private final QueryColumn queryColumn;
+
+    public NegativeQueryColumn(QueryColumn queryColumn) {
+        this.queryColumn = queryColumn;
+    }
+
+    @Override
+    public Object[] getParamValues() {
+        if (queryColumn instanceof HasParamsColumn) {
+            return ((HasParamsColumn) queryColumn).getParamValues();
+        }
+        return FlexConsts.EMPTY_ARRAY;
+    }
+
+    @Override
+    String toSelectSql(List<QueryTable> queryTables, IDialect dialect) {
+        return toConditionSql(queryTables, dialect) + WrapperUtil.buildColumnAlias(alias, dialect);
+    }
+
+    @Override
+    String toConditionSql(List<QueryTable> queryTables, IDialect dialect) {
+        return "-" + queryColumn.toConditionSql(queryTables, dialect);
+    }
+
+}

mybatis-flex-core/src/main/java/com/mybatisflex/core/query/QueryMethods.java

@@ -2408,6 +2408,13 @@ public class QueryMethods {
         return new RawQueryColumn("'" + s + "'");
     }
 
+    /**
+     * 构建相反数。
+     */
+    public static QueryColumn negative(QueryColumn queryColumn) {
+        return new NegativeQueryColumn(queryColumn);
+    }
+
     /**
      * 构建自定义列。
      */