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“INSERT IGNORE” vs “INSERT … ON DUPLICATE KEY UPDATE”
... but the values you insert don't map to a partition.
If you use REPLACE, MySQL actually does a DELETE followed by an INSERT internally, which has some unexpected side effects:
A new auto-increment ID is allocated.
Dependent rows with foreign keys may be deleted (if you use cascading foreign ke...
Cast int to varchar
... @JonathanSayce I'm not overly familiar with the ins & outs of MySQL and it might not use something arbitrary, but I wouldn't rely on the MySQL engine to be that smart (no offense to MySQL). In order to be sure you get the proper length, I would always explicitly provide one.
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海量数据相似度计算之simhash和海明距离 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...对于结果的分析。分析前我们需要对这些数据去除重复，如何选择和设 通过 采集系统 我们采集了大量文本数据，但是文本中有很多重复数据影响我们对于结果的分析。分析前我们需要对这些数据去除重复，如何选择和设计文...
Can PHP PDO Statements accept the table or column name as parameter?
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I miss mysql_real_escape_string(). Maybe here I can say it without someone jumping in and saying "But you don't need it with PDO"
– Rolf
Oct 20 '18 at 8:39
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Is the primary key automatically indexed in MySQL?
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According to http://dev.mysql.com/doc/refman/5.0/en/constraint-primary-key.html it would appear that this is would be implicit
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Linux 进程卡住了怎么办？ - 操作系统(内核) - 清泛网 - 专注C/C++及内核技术
...ffffffff>] 0xffffffffffffffff
这时候按 Ctrl+C 也不能退出。
root@localhost:~# ls /jfs
^C
^C^C^C^C^C
但是用 strace 却能唤醒它，并且开始处理之前的中断信号，然后就退出了。
root@localhost:~# strace -p `pgrep ls`
strace: Process 26469 attached
--- SI...
Convert from MySQL datetime to another format with PHP
I have a datetime column in MySQL.
18 Answers
18
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When to use Hadoop, HBase, Hive and Pig?
...ru some SQL like language
To replace daily aggregation data generated thru MySQL with Hive
Build Custom reports thru queries in Hive
Architecture Options
I benchmarked the following options:
Hive+HDFS
Hive+HBase - queries were too slow so I dumped this option
Design
Daily log Files were tr...
MySQL select one column DISTINCT, with corresponding other columns
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@Full Decent you can't, according to MySQL documentation: "The server is free to choose any value from each group, so unless they are the same, the values chosen are indeterminate.". In practice I've successfully used this kind of queries with ORDER BY clause, ...
MySQL: Large VARCHAR vs. TEXT?
I've got a messages table in MySQL which records messages between users. Apart from the typical ids and message types (all integer types) I need to save the actual message text as either VARCHAR or TEXT. I'm setting a front-end limit of 3000 characters which means the messages would never be inserte...