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SQL keys, MUL vs PRI vs UNI
...hat the field is (part of) a non-unique index. You can issue
show create table <table>;
To see more information about the table structure.
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How do I dump the data of some SQLite3 tables?
How do I dump the data, and only the data, not the schema, of some SQLite3 tables of a database (not all the tables)?
The dump should be in SQL format, as it should be easily re-entered into the database later and should be done from the command line. Something like
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Array to String PHP?
...e a DB is so you can accomplish work like this trivially. You don't need a table to store arrays, you need a table that you can represent as an array.
Example:
id | word
1 | Sports
2 | Festivals
3 | Classes
4 | Other
You would simply select the data from the table with SQL, rather than have ...
Wrap text in tag
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To Wrap TD text
First set table style
table{
table-layout: fixed;
}
then set TD Style
td{
word-wrap:break-word
}
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Rails 3: Get Random Record
...ils 3 all examples will work. But using order RANDOM is quite slow for big tables but more sql-style
UPD. You can use the following trick on an indexed column (PostgreSQL syntax):
select *
from my_table
where id >= trunc(
random() * (select max(id) from my_table) + 1
)
order by id
limit 1...
Cannot use identity column key generation with ( TABLE_PER_CLASS )
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The problem here is that you mix "table-per-class" inheritance and GenerationType.Auto.
Consider an identity column in MsSQL. It is column based. In a "table-per-class" strategy you use one table per class and each one has an ID.
Try:
@GeneratedValue(strat...
CSS: how do I create a gap between rows in a table?
Meaning making the resultant table look less like this:
12 Answers
12
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Favourite performance tuning tricks [closed]
...e following...
99% of problems I have seen are caused by putting too many tables in a join. The fix for this is to do half the join (with some of the tables) and cache the results in a temporary table. Then do the rest of the query joining on that temporary table.
Query Optimisation Checklist
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MySQL maximum memory usage
...the (f'ing) manual.
As for the database -- a few important constraints:
table engine (InnoDB, MyISAM, ...)
size
indices
usage
Most MySQL tips on stackoverflow will tell you about 5-8 so called important settings. First off, not all of them matter - e.g. allocating a lot of resources to InnoDB a...
Check if a temporary table exists and delete if it exists before creating a temporary table
I am using the following code to check if the temporary table exists and drop the table if it exists before creating again. It works fine as long as I don't change the columns. If I add a column later, it will give an error saying "invalid column". Please let me know what I am doing wrong.
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