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How should one use std::optional?
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@Rapptz Line 256: union storage_t { unsigned char dummy_; T value_; ... } Line 289: struct optional_base { bool init_; storage_t<T> storage_; ... } How is that not "a T and a bool"? I completely agree the implementation is very tricky an...
Avoid duplicates in INSERT INTO SELECT query in SQL Server
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Using NOT EXISTS:
INSERT INTO TABLE_2
(id, name)
SELECT t1.id,
t1.name
FROM TABLE_1 t1
WHERE NOT EXISTS(SELECT id
FROM TABLE_2 t2
WHERE t2.id = t1.id)
Using NOT IN:
INSERT INTO TABLE_2
(id, name)
SELECT t1.id,
t1....
What do column flags mean in MySQL Workbench?
In MySQL Workbench table editor there are 7 column flags available: PK, NN, UQ, BIN, UN, ZF, AI.
3 Answers
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Python SQL query string formatting
...qualified a somewhere between Option 2 and Option 4
Code Sample:
sql = ("SELECT field1, field2, field3, field4 "
"FROM table "
"WHERE condition1=1 "
"AND condition2=2;")
Works as well with f-strings:
fields = "field1, field2, field3, field4"
table = "table"
conditions = "co...
Unique constraint that allows empty values in MySQL
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Yes, you can do this. See the MySQL reference (version 5.5).
A UNIQUE index creates a constraint such that all values in the index must be distinct. An error occurs if you try to add a new row with a key value that matches an existing row. For all eng...
Where are my postgres *.conf files?
...alives_idle = 0 # TCP_KEEPIDLE, in seconds;
# 0 selects the system default
#tcp_keepalives_interval = 0 # TCP_KEEPINTVL, in seconds;
# 0 selects the system default
#tcp_keepalives_count = 0 # TCP_KEEPCNT;
# 0 selects the...
Can't choose class as main class in IntelliJ
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Select the folder containing the package tree of these classes, right-click and choose "Mark Directory as -> Source Root"
share
|
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Is short-circuiting logical operators mandated? And evaluation order?
... function, at least one of the arguments needs to be a class (or struct or union) or an enum, or a reference to one of those. Being POD means that you can use memcpy on it.
– Derek Ledbetter
Mar 12 '09 at 21:45
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ros 基本调试 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...的开发中，还是帮助测试ros的关键部分——你都需要了解如何生成重要的调试日志。
对于开发者来说，如果想准确地找出和判断ros的运行状态，调试信息是非常重要的。从操作系统得到默认的调试输出很容易，但是这些输出对...
BugTrap程序崩溃快照上传服务端开发配置 - C/C++ - 清泛网 - 专注C/C++及内核技术
...篇《BugTrap：程序崩溃快照、bug跟踪之利器》详细介绍了如何利用BugTrap监控程序崩溃，这里继续介绍如何将客户端的崩溃包上传至服务器端（当然前提是用户选择“发送报告”）。上一篇《BugTrap：程序崩溃快照、bug跟踪之利器》...