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How do I create a unique constraint that also allows nulls?
...et_AllowNull
UNIQUE (TicketID, TicketUnique);
If IssueID 1 has ticket 123, the UNIQUE constraint will be on values (123, NULL). If IssueID 2 has no ticket, it will be on (NULL, 2). Some thought will show that this constraint cannot be duplicated for any row in the table, and still allows multip...
Get users by name property using Firebase
...:
Write to Firebase with a unique, known key:
ref.child('users').child('123').set({ "first_name": "rob", "age": 28 })
Append to lists with an auto-generated key that will automatically sort by time written:
ref.child('users').push({ "first_name": "rob", "age": 28 })
Listen for changes in data ...
Is JavaScript an untyped language?
...licit compiler interjection, the instruction will error during run-time.
"12345" * 1 === 12345 // string * number => number
Strongly typed means there is a compiler, and it wants you an explicit cast from string to integer.
(int) "12345" * 1 === 12345
In either case, some compiler's featur...
How to convert std::string to lower case?
...aracters allowed in the french language. For instance a string 'Test String123. É Ï\n' will be converted to : 'test string123. É Ï\n' although characters É Ï and their lower case couterparts 'é' and 'ï', are allowed in french. It seems that no solution for that was provided by other message...
Fastest way to check if a string is JSON in PHP?
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$phone = '021234567'; var_dump(isJson($phone)); return true no! it should return false.
– vee
Jan 2 '14 at 17:12
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BLE（四）嗅探工具 - 创客硬件开发 - 清泛IT社区，为创新赋能！
...级关系和各字段含义
缺点：
不用指定广播信道，确实操作起来比较方便，但与之相对的是经常无法抓到后面的通信数据包。无论是作为开发用的调试工具，还是分析用的嗅探工具，都不够理想
0x2 商业侦听工具0x21 Frontline BPA®...
Cast a Double Variable to Decimal
...hould use the M when declaring a new literal decimal value:
decimal dec = 123.45M;
(Without the M, 123.45 is treated as a double and will not compile.)
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MySQL复制的概述、安装、故障、技巧、工具 - 数据库(内核) - 清泛网 - 专注...
...：
如果数据库使用的是MyISAM表类型的话，可按如下方式操作：
shell> mysqldump --all-databases --master-data=1 > data.sql
注：master-data选项缺省会打开lock-all-tables，并写入CHANGE MASTER TO语句。
如果数据库使用的是InnoDB表类型的话，则应该...
Does Javascript pass by reference? [duplicate]
...cript!
Call-by-Value
Primitive types are passed by-value:
var num = 123, str = "foo";
function f(num, str) {
num += 1;
str += "bar";
console.log("inside of f:", num, str);
}
f(num, str);
console.log("outside of f:", num, str);
Reassignments inside a function scope are ...
Difference between filter and filter_by in SQLAlchemy
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Be careful when using .filter. a query like id=12345, query(users).filter(id == id) will not filter on users.id. Instead, it will evaluate id == id as True and return all users. You need to use .filter(users.id == id) (as demoed above). I made this mistake earlier today.
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