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JOIN queries vs multiple queries
... you are joining 3 or more tables on different keys, often databases (i.e. mysql) can only use one index per table, meaning maybe one of the joins will be fast (and use an index) whereas the others will be extremely slow. For multiple queries, you can optimize the indexes to use for each query.
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那些年 O2O创业我踩了十个坑 - 资讯 - 清泛网 - 专注C/C++及内核技术
那些年 O2O创业我踩了十个坑作为创始人如何分清你的项目要不要坚持，首先要分清你做的项目是在坚持还是维持，坚持可以有明天，而维持，等待的只有败局。12月4日，黑马营第一次课程结束，为期三天的课程对我影响最大的...
What does WISC (stack) mean? [closed]
... for the software/technology bundle/stack representing Linux , Apache , MySQL , PHP . There are a few passing references on the Web that use the acronym WISC to speak of the other (supposedly Microsoft-centric) software/technology bundle/stack in contrast to LAMP. There is, however, no Wikip...
update columns values with column of another table based on condition [duplicate]
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it's not working in mysql
– cikatomo
Sep 30 '15 at 19:30
22
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On duplicate key ignore? [duplicate]
...because it will additionally hold Next-Key lock on your indexes. More: dev.mysql.com/doc/refman/5.7/en/…
– Dzmitry Lazerka
Mar 14 '17 at 7:13
1
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How to remove not null constraint in sql server using query
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Why does this work and not the above accepted answer for mysql ?
– HopeKing
Feb 13 '18 at 8:47
1
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Altering a column to be nullable
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If this was MySQL syntax, the type would have been missing, as some other responses point out.
Correct MySQL syntax would have been:
ALTER TABLE Merchant_Pending_Functions MODIFY NumberOfLocations INT NULL
Posting here for clarity to ...
Delete terminal history in Linux [closed]
...can use previous commands again. Great feature. However, I started logging mysql into mysql with the sensitive details in the command.
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Can I change a column from NOT NULL to NULL without dropping it?
... I tried with alter column and it didn't work with the latest mysql server. I tried with modify column and it worked. Strange...
– Kostas Andrianos
Aug 19 '17 at 15:29
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PHP编译configure时常见错误 - 更多技术 - 清泛网 - 专注C/C++及内核技术
...e gmp.h
centos: yum install gmp-devel
14、Configure: error: Cannot find MySQL header files under /usr. Note that the MySQL client library is not bundled anymore!
yum install mysql-devel (For Redhat & Fedora)
# apt-get install libmysql++-dev (For Ubuntu)
15、Configure: error: Please reinstall ...