Mongdb查询语法（Robomongo可视化工具）

大部分业务使用Mysql，此次业务需求用到Mongdb，将Mysql与Mongdb的语法对比起来掌握查询语法

一、查询

1、查询全表

Mysql：select * from table_name;

Mongdb：db.collection_name.find();

2、带条件查询

Mysql：select * from table_name where column_name="value";

Mongdb：db.collection_name.find({'column_name':'value'});

3、带条件查询，展示需要的字段

Mysql：select column1_name,column2_name from table_name where column_name="value";

Mongdb：db.collection_name.find({'column_name':'value'},{'column1_name':1,'column2_name':1);【第一个{} 放where条件 第二个{} 指定那些列显示和不显示 （0表示不显示 1表示显示)】

3.1、带条件查询-----等于

Mysql：select * from table_name where column_name="value";

Mongdb：db.collection_name.find({'column_name':'value'});

3.2、带条件查询-----and 

Mysql：select * from table_name where column1_name="value" and column2_name="value" ;

Mongdb：db.collection_name.find({'column_name':'value','column_name':'value'});

3.3、带条件查询----------or 

Mysql：select * from table_name where column1_name="value" or column2_name="value" ;

Mongdb：db.collection_name.find({'$or:[{'column1_name':'value'},{'column2_name':'value'}]'});

3.4、带条件查询-----<, <=, >, >= ($lt, $lte, $gt, $gte ) 

Mysql：select * from table_name where column_name>value and column_name

Mongdb：db.collection_name.find({'column_name':{'$gt':value,'$lt':value}});

3.5、带条件查询-----in, not in ($in, $nin) 

Mysql：select * from table_name where column_name IN("value1","value2");

Mongdb：db.collection_name.find({'column_name ':{'$in:[value1,value2]'}});

3.6、带条件查询-----匹配null 

Mysql：select * from table_name where column_name is NULL;

Mongdb：db.collection_name.find({'column_name ':null});

3.7、带条件查询-----like (mongoDB 支持正则表达式) 

Mysql：select * from table_name where column_name like '%value%';

             select * from table_name where column_name like 'value%';

             select * from table_name where column_name like '%value';

Mongdb：db.collection_name.find({'column_name':/value/}); 

                db.collection_name.find({'column_name':/^value/}); 

                db.collection_name.find({'column_name':/value$/});

3.8、带条件查询-----distinct 

Mysql：select distinct  column_name from table_name;

Mongdb：db.collection_name.distinct('column_name');

3.8、带条件查询-----count

Mysql：select count(*) from table_name;

Mongdb：db.collection_name.count();

db.collection_name.count({'column1_name':'column1_value','column2_name':'column2_value'});