MySQL 5.7 reference about JSON
最近需要用到MySQL 5.7中的JSON,总结一下MySQL中关于JSON的内容
参考:
JSON Function Reference
Functions That Create JSON Values
JSON_ARRAY([val[, val] ...])
构造并返回一个JSON数组
mysql> SELECT JSON_ARRAY(1, "abc", NULL, TRUE, CURTIME());
+---------------------------------------------+
| JSON_ARRAY(1, "abc", NULL, TRUE, CURTIME()) |
+---------------------------------------------+
| [1, "abc", null, true, "11:30:24.000000"] |
+---------------------------------------------+
JSON_OBJECT([key, val[, key, val] ...])
通过键值对列表返回一个JSON对象
mysql> SELECT JSON_OBJECT('id', 87, 'name', 'carrot');
+-----------------------------------------+
| JSON_OBJECT('id', 87, 'name', 'carrot') |
+-----------------------------------------+
| {"id": 87, "name": "carrot"} |
+-----------------------------------------+
JSON_QUOTE(json_val)
产生JSON字符串
mysql> SELECT JSON_QUOTE('null'), JSON_QUOTE('"null"');
+--------------------+----------------------+
| JSON_QUOTE('null') | JSON_QUOTE('"null"') |
+--------------------+----------------------+
| "null" | "\"null\"" |
+--------------------+----------------------+
mysql> SELECT JSON_QUOTE('[1, 2, 3]');
+-------------------------+
| JSON_QUOTE('[1, 2, 3]') |
+-------------------------+
| "[1, 2, 3]" |
+-------------------------+
Functions That Search JSON Values
JSON_CONTAINS(json_doc, val[, path])
返回0 or 1来表示一个特定的值是否在目标JSON文档中
mysql> SET @j = '{"a": 1, "b": 2, "c": {"d": 4}}';
mysql> SET @j2 = '';
mysql> SELECT JSON_CONTAINS(@j, @j2, '$.a');
+-------------------------------+
| JSON_CONTAINS(@j, @j2, '$.a') |
+-------------------------------+
| 1 |
+-------------------------------+
mysql> SELECT JSON_CONTAINS(@j, @j2, '$.b');
+-------------------------------+
| JSON_CONTAINS(@j, @j2, '$.b') |
+-------------------------------+
| 0 |
+-------------------------------+ mysql> SET @j2 = '{"d": 4}';
mysql> SELECT JSON_CONTAINS(@j, @j2, '$.a');
+-------------------------------+
| JSON_CONTAINS(@j, @j2, '$.a') |
+-------------------------------+
| 0 |
+-------------------------------+
mysql> SELECT JSON_CONTAINS(@j, @j2, '$.c');
+-------------------------------+
| JSON_CONTAINS(@j, @j2, '$.c') |
+-------------------------------+
| 1 |
+-------------------------------+
JSON_CONTAINS_PATH(json_doc, one_or_all, path[, path] ...)
返回0 or 1来表示一个JSON文档是否包含一个或多个给定的数据
参数:
- 'one': 1 if at least one path exists within the document, 0 otherwise.
- 'all': 1 if all paths exist within the document, 0 otherwise.
mysql> SET @j = '{"a": 1, "b": 2, "c": {"d": 4}}';
mysql> SELECT JSON_CONTAINS_PATH(@j, 'one', '$.a', '$.e');
+---------------------------------------------+
| JSON_CONTAINS_PATH(@j, 'one', '$.a', '$.e') |
+---------------------------------------------+
| 1 |
+---------------------------------------------+
mysql> SELECT JSON_CONTAINS_PATH(@j, 'all', '$.a', '$.e');
+---------------------------------------------+
| JSON_CONTAINS_PATH(@j, 'all', '$.a', '$.e') |
+---------------------------------------------+
| 0 |
+---------------------------------------------+
mysql> SELECT JSON_CONTAINS_PATH(@j, 'one', '$.c.d');
+----------------------------------------+
| JSON_CONTAINS_PATH(@j, 'one', '$.c.d') |
+----------------------------------------+
| 1 |
+----------------------------------------+
mysql> SELECT JSON_CONTAINS_PATH(@j, 'one', '$.a.d');
+----------------------------------------+
| JSON_CONTAINS_PATH(@j, 'one', '$.a.d') |
+----------------------------------------+
| 0 |
+----------------------------------------+
JSON_EXTRACT(json_doc, path[, path] ...)
从JSON文档返回数据,注意5.7.9以上用->代替
mysql> SELECT c, JSON_EXTRACT(c, "$.id"), g
> FROM jemp
> WHERE JSON_EXTRACT(c, "$.id") > 1
> ORDER BY JSON_EXTRACT(c, "$.name");
+-------------------------------+-----------+------+
| c | c->"$.id" | g |
+-------------------------------+-----------+------+
| {"id": "3", "name": "Barney"} | "3" | 3 |
| {"id": "4", "name": "Betty"} | "4" | 4 |
| {"id": "2", "name": "Wilma"} | "2" | 2 |
+-------------------------------+-----------+------+
3 rows in set (0.00 sec) mysql> SELECT c, c->"$.id", g
> FROM jemp
> WHERE c->"$.id" > 1
> ORDER BY c->"$.name";
+-------------------------------+-----------+------+
| c | c->"$.id" | g |
+-------------------------------+-----------+------+
| {"id": "3", "name": "Barney"} | "3" | 3 |
| {"id": "4", "name": "Betty"} | "4" | 4 |
| {"id": "2", "name": "Wilma"} | "2" | 2 |
+-------------------------------+-----------+------+
3 rows in set (0.00 sec)
->符号可以用在非select中,表示某个JSON key的value
mysql> ALTER TABLE jemp ADD COLUMN n INT;
Query OK, 0 rows affected (0.68 sec)
Records: 0 Duplicates: 0 Warnings: 0 mysql> UPDATE jemp SET n=1 WHERE c->"$.id" = "4";
Query OK, 1 row affected (0.04 sec)
Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT c, c->"$.id", g, n
> FROM jemp
> WHERE JSON_EXTRACT(c, "$.id") > 1
> ORDER BY c->"$.name";
+-------------------------------+-----------+------+------+
| c | c->"$.id" | g | n |
+-------------------------------+-----------+------+------+
| {"id": "3", "name": "Barney"} | "3" | 3 | NULL |
| {"id": "4", "name": "Betty"} | "4" | 4 | 1 |
| {"id": "2", "name": "Wilma"} | "2" | 2 | NULL |
+-------------------------------+-----------+------+------+
3 rows in set (0.00 sec) mysql> DELETE FROM jemp WHERE c->"$.id" = "4";
Query OK, 1 row affected (0.04 sec) mysql> SELECT c, c->"$.id", g, n
> FROM jemp
> WHERE JSON_EXTRACT(c, "$.id") > 1
> ORDER BY c->"$.name";
+-------------------------------+-----------+------+------+
| c | c->"$.id" | g | n |
+-------------------------------+-----------+------+------+
| {"id": "3", "name": "Barney"} | "3" | 3 | NULL |
| {"id": "2", "name": "Wilma"} | "2" | 2 | NULL |
+-------------------------------+-----------+------+------+
2 rows in set (0.00 sec)
->符号还可以用在json数组中
mysql> CREATE TABLE tj10 (a JSON, b INT);
Query OK, 0 rows affected (0.26 sec) mysql> INSERT INTO tj10
> VALUES ("[3,10,5,17,44]", 33), ("[3,10,5,17,[22,44,66]]", 0);
Query OK, 1 row affected (0.04 sec) mysql> SELECT a->"$[]" FROM tj10;
+--------------+
| a->"$[]" |
+--------------+
| 44 |
| [22, 44, 66] |
+--------------+
2 rows in set (0.00 sec) mysql> SELECT * FROM tj10 WHERE a->"$[]" = 3;
+------------------------------+------+
| a | b |
+------------------------------+------+
| [3, 10, 5, 17, 44] | 33 |
| [3, 10, 5, 17, [22, 44, 66]] | 0 |
+------------------------------+------+
2 rows in set (0.00 sec)
->符号如果没有匹配的key,可以用NULL表示
mysql> SELECT * FROM tj10 WHERE a->"$[][]" IS NOT NULL;
+------------------------------+------+
| a | b |
+------------------------------+------+
| [3, 10, 5, 17, [22, 44, 66]] | 0 |
+------------------------------+------+ mysql> SELECT a->"$[][]" FROM tj10;
+--------------+
| a->"$[][]" |
+--------------+
| NULL |
| 44 |
+--------------+
2 rows in set (0.00 sec)
JSON_KEYS(json_doc[, path])
列出所有KEY或指定KEY
mysql> SELECT JSON_KEYS('{"a": 1, "b": {"c": 30}}');
+---------------------------------------+
| JSON_KEYS('{"a": 1, "b": {"c": 30}}') |
+---------------------------------------+
| ["a", "b"] |
+---------------------------------------+
mysql> SELECT JSON_KEYS('{"a": 1, "b": {"c": 30}}', '$.b');
+----------------------------------------------+
| JSON_KEYS('{"a": 1, "b": {"c": 30}}', '$.b') |
+----------------------------------------------+
| ["c"] |
+----------------------------------------------+
JSON_SEARCH(json_doc, one_or_all, search_str[, escape_char[, path] ...])
查找元素,返回位置
'one'
: The search terminates after the first match and returns one path string. It is undefined which match is considered first.'all'
: The search returns all matching path strings such that no duplicate paths are included. If there are multiple strings, they are autowrapped as an array. The order of the array elements is undefined.
mysql> SET @j = '["abc", [{"k": "10"}, "def"], {"x":"abc"}, {"y":"bcd"}]'; mysql> SELECT JSON_SEARCH(@j, 'one', 'abc');
+-------------------------------+
| JSON_SEARCH(@j, 'one', 'abc') |
+-------------------------------+
| "$[]" |
+-------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', 'abc');
+-------------------------------+
| JSON_SEARCH(@j, 'all', 'abc') |
+-------------------------------+
| ["$[0]", "$[].x"] |
+-------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', 'ghi');
+-------------------------------+
| JSON_SEARCH(@j, 'all', 'ghi') |
+-------------------------------+
| NULL |
+-------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '');
+------------------------------+
| JSON_SEARCH(@j, 'all', '') |
+------------------------------+
| "$[][].k" |
+------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '', NULL, '$');
+-----------------------------------------+
| JSON_SEARCH(@j, 'all', '', NULL, '$') |
+-----------------------------------------+
| "$[][].k" |
+-----------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '', NULL, '$[*]');
+--------------------------------------------+
| JSON_SEARCH(@j, 'all', '', NULL, '$[*]') |
+--------------------------------------------+
| "$[][].k" |
+--------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '', NULL, '$**.k');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', '', NULL, '$**.k') |
+---------------------------------------------+
| "$[][].k" |
+---------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '', NULL, '$[*][0].k');
+-------------------------------------------------+
| JSON_SEARCH(@j, 'all', '', NULL, '$[*][0].k') |
+-------------------------------------------------+
| "$[][].k" |
+-------------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '', NULL, '$[1]');
+--------------------------------------------+
| JSON_SEARCH(@j, 'all', '', NULL, '$[1]') |
+--------------------------------------------+
| "$[][].k" |
+--------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '', NULL, '$[1][0]');
+-----------------------------------------------+
| JSON_SEARCH(@j, 'all', '', NULL, '$[1][0]') |
+-----------------------------------------------+
| "$[][].k" |
+-----------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', 'abc', NULL, '$[2]');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', 'abc', NULL, '$[2]') |
+---------------------------------------------+
| "$[].x" |
+---------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '%a%');
+-------------------------------+
| JSON_SEARCH(@j, 'all', '%a%') |
+-------------------------------+
| ["$[0]", "$[].x"] |
+-------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '%b%');
+-------------------------------+
| JSON_SEARCH(@j, 'all', '%b%') |
+-------------------------------+
| ["$[0]", "$[].x", "$[].y"] |
+-------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', NULL, '$[0]');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', NULL, '$[0]') |
+---------------------------------------------+
| "$[]" |
+---------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', NULL, '$[2]');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', NULL, '$[2]') |
+---------------------------------------------+
| "$[].x" |
+---------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', NULL, '$[1]');
+---------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', NULL, '$[1]') |
+---------------------------------------------+
| NULL |
+---------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', '', '$[1]');
+-------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', '', '$[1]') |
+-------------------------------------------+
| NULL |
+-------------------------------------------+ mysql> SELECT JSON_SEARCH(@j, 'all', '%b%', '', '$[3]');
+-------------------------------------------+
| JSON_SEARCH(@j, 'all', '%b%', '', '$[3]') |
+-------------------------------------------+
| "$[].y" |
+-------------------------------------------+
Functions That Modify JSON Values
JSON_ARRAY_APPEND(json_doc, path, val[, path, val] ...)
在JSON数组指定位置追加元素,并返回结果
mysql> SET @j = '["a", ["b", "c"], "d"]';
mysql> SELECT JSON_ARRAY_APPEND(@j, '$[1]', 1);
+----------------------------------+
| JSON_ARRAY_APPEND(@j, '$[1]', 1) |
+----------------------------------+
| ["a", ["b", "c", 1], "d"] |
+----------------------------------+
mysql> SELECT JSON_ARRAY_APPEND(@j, '$[0]', 2);
+----------------------------------+
| JSON_ARRAY_APPEND(@j, '$[0]', 2) |
+----------------------------------+
| [["a", 2], ["b", "c"], "d"] |
+----------------------------------+
mysql> SELECT JSON_ARRAY_APPEND(@j, '$[1][0]', 3);
+-------------------------------------+
| JSON_ARRAY_APPEND(@j, '$[1][0]', 3) |
+-------------------------------------+
| ["a", [["b", 3], "c"], "d"] |
+-------------------------------------+ mysql> SET @j = '{"a": 1, "b": [2, 3], "c": 4}';
mysql> SELECT JSON_ARRAY_APPEND(@j, '$.b', 'x');
+------------------------------------+
| JSON_ARRAY_APPEND(@j, '$.b', 'x') |
+------------------------------------+
| {"a": 1, "b": [2, 3, "x"], "c": 4} |
+------------------------------------+
mysql> SELECT JSON_ARRAY_APPEND(@j, '$.c', 'y');
+--------------------------------------+
| JSON_ARRAY_APPEND(@j, '$.c', 'y') |
+--------------------------------------+
| {"a": 1, "b": [2, 3], "c": [4, "y"]} |
+--------------------------------------+ mysql> SET @j = '{"a": 1}';
mysql> SELECT JSON_ARRAY_APPEND(@j, '$', 'z');
+---------------------------------+
| JSON_ARRAY_APPEND(@j, '$', 'z') |
+---------------------------------+
| [{"a": 1}, "z"] |
+---------------------------------+
JSON_ARRAY_INSERT(json_doc, path, val[, path, val] ...)
在JSON数组指定位置插入元素,并返回结果
mysql> SET @j = '["a", {"b": [1, 2]}, [3, 4]]';
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[1]', 'x');
+------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[1]', 'x') |
+------------------------------------+
| ["a", "x", {"b": [1, 2]}, [3, 4]] |
+------------------------------------+
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[100]', 'x');
+--------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[100]', 'x') |
+--------------------------------------+
| ["a", {"b": [1, 2]}, [3, 4], "x"] |
+--------------------------------------+
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[1].b[0]', 'x');
+-----------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[1].b[0]', 'x') |
+-----------------------------------------+
| ["a", {"b": ["x", 1, 2]}, [3, 4]] |
+-----------------------------------------+
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[2][1]', 'y');
+---------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[2][1]', 'y') |
+---------------------------------------+
| ["a", {"b": [1, 2]}, [3, "y", 4]] |
+---------------------------------------+
mysql> SELECT JSON_ARRAY_INSERT(@j, '$[0]', 'x', '$[2][1]', 'y');
+----------------------------------------------------+
| JSON_ARRAY_INSERT(@j, '$[0]', 'x', '$[2][1]', 'y') |
+----------------------------------------------------+
| ["x", "a", {"b": [1, 2]}, [3, 4]] |
+----------------------------------------------------+
JSON_INSERT(json_doc, path, val[, path, val] ...)
若键值对不在JSON对象中,则插入并返回
mysql> SET @j = '{ "a": 1, "b": [2, 3]}';
mysql> SELECT JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]');
+----------------------------------------------------+
| JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]') |
+----------------------------------------------------+
| {"a": 1, "b": [2, 3], "c": "[true, false]"} |
+----------------------------------------------------+
JSON_MERGE(json_doc, json_doc[, json_doc] ...)
合并json数据并返回结果
mysql> SELECT JSON_MERGE('[1, 2]', '[true, false]');
+---------------------------------------+
| JSON_MERGE('[1, 2]', '[true, false]') |
+---------------------------------------+
| [1, 2, true, false] |
+---------------------------------------+
mysql> SELECT JSON_MERGE('{"name": "x"}', '{"id": 47}');
+-------------------------------------------+
| JSON_MERGE('{"name": "x"}', '{"id": 47}') |
+-------------------------------------------+
| {"id": 47, "name": "x"} |
+-------------------------------------------+
mysql> SELECT JSON_MERGE('', 'true');
+-------------------------+
| JSON_MERGE('', 'true') |
+-------------------------+
| [1, true] |
+-------------------------+
mysql> SELECT JSON_MERGE('[1, 2]', '{"id": 47}');
+------------------------------------+
| JSON_MERGE('[1, 2]', '{"id": 47}') |
+------------------------------------+
| [1, 2, {"id": 47}] |
+------------------------------------+
JSON_REMOVE(json_doc, path[, path] ...)
删除并返回结果
mysql> SET @j = '["a", ["b", "c"], "d"]';
mysql> SELECT JSON_REMOVE(@j, '$[1]');
+-------------------------+
| JSON_REMOVE(@j, '$[1]') |
+-------------------------+
| ["a", "d"] |
+-------------------------+
JSON_REPLACE(json_doc, path, val[, path, val] ...)
替换并返回结果,如果不存在则无操作
mysql> SET @j = '{ "a": 1, "b": [2, 3]}';
mysql> SELECT JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]');
+-----------------------------------------------------+
| JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]') |
+-----------------------------------------------------+
| {"a": 10, "b": [2, 3]} |
+-----------------------------------------------------+
JSON_SET(json_doc, path, val[, path, val] ...)
set insert replace三者比较
- JSON_SET() replaces existing values and adds nonexisting values.
- JSON_INSERT() inserts values without replacing existing values.
- JSON_REPLACE() replaces only existing values.
mysql> SET @j = '{ "a": 1, "b": [2, 3]}';
mysql> SELECT JSON_SET(@j, '$.a', 10, '$.c', '[true, false]');
+-------------------------------------------------+
| JSON_SET(@j, '$.a', 10, '$.c', '[true, false]') |
+-------------------------------------------------+
| {"a": 10, "b": [2, 3], "c": "[true, false]"} |
+-------------------------------------------------+
mysql> SELECT JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]');
+----------------------------------------------------+
| JSON_INSERT(@j, '$.a', 10, '$.c', '[true, false]') |
+----------------------------------------------------+
| {"a": 1, "b": [2, 3], "c": "[true, false]"} |
+----------------------------------------------------+
mysql> SELECT JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]');
+-----------------------------------------------------+
| JSON_REPLACE(@j, '$.a', 10, '$.c', '[true, false]') |
+-----------------------------------------------------+
| {"a": 10, "b": [2, 3]} |
+-----------------------------------------------------+
Functions That Return JSON Value Attributes
返回JSON相关属性,不常用,直接参考文档
MySQL 5.7 reference about JSON的更多相关文章
- MySQL :: MySQL 5.0 Reference Manual :: 14.4 The MEMORY (HEAP) Storage Engine
MySQL :: MySQL 5.0 Reference Manual :: 14.4 The MEMORY (HEAP) Storage Engine The MEMORY (HEAP) Stora ...
- 使用python将mysql数据库的数据转换为json数据
由于产品运营部需要采用第三方个推平台,来推送消息.如果手动一个个键入字段和字段值,容易出错,且非常繁琐,需要将mysql的数据转换为json数据,直接复制即可. 本文将涉及到如何使用Python访问M ...
- MySQL 5.7 Reference Manual :: 4.5.4 mysqldump & mysql — Database Backup & Restore Program
MySQL :: MySQL 5.7 Reference Manual :: 4.5.4 mysqldump — A Database Backup Programhttps://dev.mysql. ...
- MySQL :: MySQL 8.0 Reference Manual :: B.6.4.3 Problems with NULL Values https://dev.mysql.com/doc/refman/8.0/en/problems-with-null.html
MySQL :: MySQL 8.0 Reference Manual :: B.6.4.3 Problems with NULL Values https://dev.mysql.com/doc/r ...
- [转帖 ]MySQL 5.7 新特性 JSON
MySQL 5.7 新特性 JSON 的创建,插入,查询,更新 作者: 我不是鱼 (2016-08-31 16:13)分类: MySQL 标签: MySQL JSON MySQL JSON 应用 ...
- MySQL 5.7开始支持JSON,那还有必要使用MongoDB存JSON吗?请列出你的观点/理由。
一.观点A:支持MySQL存储JSON MongoDB不支持事务,而MySQL支持事务 MySQL相对MongoDB而言,MySQL的稳定性要优于MongoDB MySQL支持多种存储引擎 二.观点B ...
- VSCode package.json warning: Problems loading reference 'https://json.schemastore.org/package'...
报错内容 Problems loading reference 'https://json.schemastore.org/package': Unable to load schema from ' ...
- #MySQL 5.7.8 支持Json类型
As of MySQL 5.7.8, MySQL supports a native JSON data type that enables efficient access to data in J ...
- MySQL 5.7 深度解析: JSON数据类型使用
http://www.actionsky.com/docs/archives/156 2015年12月25日 杨涛涛 JSON (JavaScriptObject Notation) 是一种轻量级 ...
随机推荐
- JS预览图像
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <hea ...
- IBM开发者 JSON 教程
在异步应用程序中发送和接收信息时,可以选择以纯文本和 XML 作为数据格式.掌握 Ajax 的这一期讨论另一种有用的数据格式 JavaScript Object Notation(JSON),以及如何 ...
- Adapter的getView方法详解
来自:http://blog.csdn.net/yelbosh/article/details/7831812 BaseAdapter就Android应用程序中经常用到的基础数据适配器,它的主要用途是 ...
- Python学习教程(learning Python)--2 Python简单函数设计
本节讨论Python程序设计时为何引入函数? 为何大家都反对用一堆堆的单个函数语句完成一项程序的设计任务呢? 用一条条的语句去完成某项程序设计时,冗长.不宜理解,不宜复用,而采用按功能模块划分成函数, ...
- HTML5的placeholder属性如何实现换行
在HTML5中,placeholder是一个非常有用的属性,当控件中无内容时可以代替UI控件的提示功能,而不需要写额外的代码.但如果有一个textarea控件,我们需要多行的文本提示信息时,使用”\n ...
- Android--PullToRefreshListView 的简单使用
原文: http://blog.csdn.net/lmj623565791/article/details/38238749; pull-to-refresh对ListView进行了封装,叫做:Pu ...
- android-监听网络状态
1.注册一个广播接收器,监听网络状态private void Start() { IntentFilter filter = new IntentFilter(); filter.addAction( ...
- IBM MQ扩大队列最大消息长度
要设置MQ的最大消息长度,需要考虑同时设置队列管理,队列以及通道的最大消息长度. 具体操作如下: runmqsc 队列管理器名称 alter qmgr maxmsgl(10000000) 1 : al ...
- 【转】VNC配置
配置VNC服务参数文件 编辑vncservers文件追加如下 #vi /etc/sysconfig/vncsevers VNCSERVERS="1:root" VNCSERVERA ...
- linq里的select和selectmany操作
Select() 和 SelectMany() 的工作都是依据源值生成一个或多个结果值.Select() 为每个源值生成一个结果值.因此,总体结果是一个与源集合具有相同元素数目的集合.与之相反,Sel ...