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MySQL - How to select data by string length
Is there a MySQL function to do this (of course instead of string_length )?
6 Answers
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MySQL Select all columns from one table and some from another table
...mns from one table and just some columns from another table using JOIN? In MySQL.
4 Answers
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MySQL foreign key constraints, cascade delete
... When creating the tables, you need to specify InnoDB or another MySQL engine that's capable of CASCADE operations. Otherwise the MySQL default, MyISAM, will be used and MyISAM does not support CASCADE operations. To do this, just add ENGINE InnoDB before the last ;.
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Are there disadvantages to using a generic varchar(255) for all text-based fields?
...ould always store 255 characters.
But since you tagged this question with MySQL, I'll mention a MySQL-specific tip: as rows are copied from the storage engine layer to the SQL layer, VARCHAR fields are converted to CHAR to gain the advantage of working with fixed-width rows. So the strings in mem...
MySQL Results as comma separated list
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The intent is fine and MySQL will allow this, but be careful (generally) with your use of GROUP BY. The items in the select list need to be valid aggregates in the context of the GROUP BY clause. In this case, p.name is not strictly valid. Any d...
Get environment variable value in Dockerfile
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add -e key for passing environment variables to container.
example:
$ MYSQLHOSTIP=$(sudo docker inspect -format="{{ .NetworkSettings.IPAddress }}" $MYSQL_CONRAINER_ID)
$ sudo docker run -e DBIP=$MYSQLHOSTIP -i -t myimage /bin/bash
root@87f235949a13:/# echo $DBIP
172.17.0.2
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Can you get DB username, pw, database name in Rails?
...%
require 'parseconfig'
c=ParseConfig.new('../../.my.cnf') %>
mysqlevn: &mysql
adapter: mysql
username: <%= c.params['client']['user'] %>
password: <%= c.params['client']['password'] %>
host: localhost
socket: <%= [
'/var/run/mysqld/mysqld.sock',
'/va...
Table is marked as crashed and should be repaired
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Run this from your server's command line:
mysqlcheck --repair --all-databases
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ZMQ: 基本原理 - 开源 & Github - 清泛网 - 专注C++内核技术
...的一个。 本文的目的是解释ØMQ架构的基本概念，它们是如何组合起来的，以及它们被如此设计的原因。 拓扑 拓扑是ØMQ最主要的概念，除非你知道“拓扑”代表什么，否则将与其他概念混淆更难理解，甚至理解不当。 按...
SQL UPDATE SET one column to be equal to a value in a related table referenced by a different column
... Having a problem with a similar situation in PhpMyAdmin over MySQL. In my case, the source and destination columns are in the same table, but record selection is based on the other table. The "SELECT" version of the query works, but the UPDTATE statement throws a syntax error at "FRO...