mybatis plus 使用 QueryWrapper总结

1、select使用count函数

QueryWrapper<GeoAssoc> countWrapper = new QueryWrapper<>();
countWrapper.in("parent_geo_id", geoIds);
countWrapper.groupBy("parent_geo_id");
countWrapper.select("parent_geo_id as parentGeoId","count(*) as count");
List<Map<String, Object>> listMaps = listMaps(countWrapper);
Map<String, Long> subNodeAmountMap = listMaps.stream().collect(Collectors.toMap(e-> (String) e.get("parentGeoId"), e-> (Long) e.get("count")));

2、常用方法总结

3、LambdaQueryWrapper 查询条件同时使用 and 和 or sql 写法：

DELETE 
FROM
	Permission_Menu_Rel 
WHERE
	permissionId = 'permissionId'  
	AND (
		( sysId = 'sysId1'  AND  menuId IN ( '' menuId1, 'menuId2' ) ) 
		OR 
		( sysId = 'sysId2'  AND  menuId IN ( '' menuId3, 'menuId3' ) ) 
	);

mybatis plus LambdaQueryWrapper 写法：

public void removePermissionMenu(String permissionId, Map<String, List<String>> relSysMenuMap) {
	if (StringUtils.isBlank(permissionId) || UtilValidate.isEmpty(relSysMenuMap)) {
		return ;
	}
	
    LambdaQueryWrapper<PermissionMenuRel> queryWrapper = new LambdaQueryWrapper<>();
	queryWrapper.eq(PermissionMenuRel:: getPermissionId, permissionId);
	queryWrapper.and(qw -> {
		relSysMenuMap.forEach((systemId,menuIds) -> {
			if (StringUtils.isNotBlank(systemId) && UtilValidate.isNotEmpty(menuIds)) {
				queryWrapper.or(mqw -> mqw.eq(PermissionMenuRel:: getSystemId, systemId).in(PermissionMenuRel:: getMenud, menuIds));
			}
		});
	});

    remove(queryWrapper);

原文链接：blog.csdn.net/weixin_4048…