I would just like to ask a somewhat not so intelligent question. What
is the downside of indexing almost all of the fields in a table? Is it
advisable?
Indexes have to be built
They also consume disk space, so if you're tight on hard drives, they
might put you over the top.
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Scott
procedures
and triggers, and 5.0.15-max so I can play with even more new features
(like the Federated engine). I ought to have 4.0 on here too, since
that's what our production environment uses.
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How long should it take to insert approx 30,000 rows into MySQL.
Depends on the data and field structure. Do you have lots of indexes
on the table?
It takes me about 30 mins.
There are some tips at http://dev.mysql.com/doc/refman/4.1/en/insert-speed.html
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BY `timestamp`
DESC LIMIT 100;
DELETE FROM `table` WHERE `timestamp` @theDeadline;
It might not be quite perfect if certain critical records have the
same timestamp, but it will work in most cases.
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select * from table1 t1 left join table2 t2 on t1.date1=t2.date2 where
t2.date2 is null
where t2.name='Smith'
Maybe this?
select * from table1 t1 left join table2 t2 on t1.date1 = t2.date2 AND
t2.name = 'Smith' WHERE t2.date2 is null;
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Why isn't there a way to reference column aliases in the columns list or
where clause?
http://dev.mysql.com/doc/refman/5.0/en/problems-with-alias.html
That's why.
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Has anyone been involved with the 5.0 certification program.
I've read that the new MySQL 5 certificates will be available about 2
or 3 months after MySQL 5 becomes a Production Release.
http://db4free.blogspot.com/2005/10/mysql-5-certifications.html
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appropriate.
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I have a table like this :
name, email_1, email_2
and I want to display in a web page
name, email_1 if it exists, or email_2 if email_1 do NOT exist.
SELECT name, IF(email_1 IS NOT NULL AND email_1 != '', email_1,
email_2) AS email FROM theTable;
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We did a mysqldump to produce a transport file
from version 3 of mysql to insert the data into version 4 of mysql.
The encoded numbers were munged, presumably because they were
binary data in the dump.
Isn't this what the --hex-blob option to mysqldump is for?
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Isn't this what the --hex-blob option to mysqldump is for?
There is no such option to mysqldump in version 4.1.11.
From the manual:
--hex-blob
Dump binary string columns using hexadecimal notation (for example,
'abc' becomes 0x616263). The affected columns are BINARY, VARBINARY,
and BLOB
So now my question... is it possible that MySQL didn't execute that first
UPDATE query on that first page until after the rest of the process completed?
- The customer page is a basic form that posts the information to itself
with a simple UPDATE command and then goes to the next page.
2005-08-30 13:50.05 this is the text content
(i) sort the returned rows in order (latest first)
http://dev.mysql.com/doc/mysql/en/sorting-rows.html
(ii) be able to extract the individual parts of the date and display them in
UK format (ddmm)
mysql create table prova (`Termination ` int);
ERROR 1166: Incorrect column name 'Termination '
The manual says:
Database, table, and column names should not end with space characters.
http://dev.mysql.com/doc/mysql/en/legal-names.html
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Warning: mysql_query(): supplied argument is not a valid MySQL-Link resource
in /srv/www/htdocs/web1/html/inc/class/sql.php on line 88
I would guess that there is some problem with the syntax of your SQL.
If you make it a habit to do queries like this:
$sql = SELECT * FROM table;
$result =
Can anyone explain why this SQL statement would fail? A friend was asked it
in a pre-interview assessment and it threw him a bit.
SELECT T1.BldgName T1.StreetName, T1.Locality, T1.PostTown from PstlAddr T1
Where T1.City='London' AND NOT EXISTS (SELECT T2.Pstl_Address_PK from
PrsnAddress T2)
I've got two columns, one is 'integer' (and store negative value), the
other one 'tinyint unsigned' (only 1 stored in it), when I multiply
these columns, quantity with negative value does not show up.
(I expect -50*10 to give : -500, but the field stay blank.)
I've look a bit at the
Select s.StudentID, s.StudentName from Student s, SubjectGrade sg where
s.StudentID = sg.StudentID and sg.Subject = 'Maths' and sg.Subject = 'Chem'
and sg.Grade = 'A'
Take a close look at the WHERE clause: sg.Subject = 'Maths' and
sg.Subject = 'Chem' will never return a result - how could the
SELECT s.StudentID, StudentName
FROM Student s
JOIN StudentGrade sg1 USING (StudentID)
JOIN StudentGrade sg2 USING (StudentID)
WHERE
sg1.Subject = 'Maths' AND sg1.Grade = 'A'
AND sg2.Subject = 'Chem' AND sg2.Grade = 'A'
So i have to write 3 join if I have 3 conditions and so on,
Shipped Undelivered Returned Open
12/8/2005 143 3 3
Does this mean of the 14 shipped on 12/8/2005, 3 were returned at some
later date, or does it mean that you shipped 14 on 12/8/2005, and on
that same day 3 unrelated shipments came back, each of which
mysql Ver 12.22 Distrib 4.0.20, for mandrake-linux-gnu (i586)
With 4.1, it might have been a little easier using some subqueries.
But with 4.0, I don't think we can get the results you're looking for
in a single query, without some really nasty setup. Part of the issue
is that we need to join
It appears that you don't need to
specify in the Group By clause all the columns that are referenced without
an aggregate function
True.
For example this query would be invalid in MSSQL but
valid in MySQL:
select id, vendor, sum(price)
from p
group by id
In this case, `vendor` would
mysqldump bundled with 5.0.10 does not seem to support
the above features.
http://dev.mysql.com/doc/mysql/en/mysqldump.html lists triggers in
5.0.11. I see no mention there of functions or stored procedures.
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To
Yes, using symbolic links.
http://dev.mysql.com/doc/mysql/en/windows-symbolic-links.html
On 8/8/05, l'[EMAIL PROTECTED] [EMAIL PROTECTED] wrote:
I installed Mysql on windows and found out that the documentation does not
talk about installing the database in another directory or partition of the
Is this what you're after?
SELECT
COUNT(*) AS members,
SUM(IF(payment_type = 'creditcard', 1, 0)) AS pay_by_card
FROM
members
JOIN payments USING (memno)
GROUP BY group;
On 8/5/05, Russell Horn [EMAIL PROTECTED] wrote:
I'm having difficulty writing a query as follows. I'm unsure
You're looking for the rows containing the group-wise maximum.
There's an explanation in the manual, section 3.6.4,
http://dev.mysql.com/doc/mysql/en/example-maximum-column-group-row.html
On 8/5/05, Kemin Zhou [EMAIL PROTECTED] wrote:
I have a simple table
col1 col2col3
A 2
SELECT col1, MAX(col2), col3 FROM table GROUP BY col1;
Because col3 is not part of the GROUP BY clause, this query will not
guarantee that the col3 returned is associated with the col2 returned.
In other words, running this query on the table containing
col1 / col2 / col3
1 11
1
mysql SELECT VERSION();
+---+
| VERSION() |
+---+
| 4.1.7-nt |
+---+
1 row in set (0.00 sec)
mysql CREATE TABLE test (col1 INT, col2 INT, col3 INT);
Query OK, 0 rows affected (0.08 sec)
mysql INSERT INTO test VALUES (1, 1, 1), (1, 2, 3);
Query OK, 2 rows affected (0.02
Here's one (not very clean, but it works) way to do it:
SELECT id, params FROM table GROUP BY params;
The trouble is, how do you know which id should come with it? If you table is
id param
1 1
2 1
should the query return
1, 1
or
2, 1
?
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From http://dev.mysql.com/doc/mysql/en/union.html :
Before MySQL 4.1.1, a limitation of UNION is that only the values
from the first SELECT are used to determine result column types and
lengths. This could result in value truncation if, for example, the
first SELECT retrieves shorter values than
1) For what I see on the MySQL manual you can have an Auto Increment not
null Field as the primary key. Say that you have a table with only
two columns the first being an Auto_Increment. How do I write an INSERT
or REPLACE SQL statement to insert data on this table? Can
I write it so that it
Is this what you had in mind? It assumes MySQL version 4.1 or later:
SELECT
id,
price -
(SELECT
SUM(IF(type = 'PAID', amount, 0 - amount))
FROM payment py
WHERE py.id http://py.id = pr.id http://pr.id)
AS balance
FROM
price pr;
On 8/4/05, Yesmin Patwary [EMAIL PROTECTED] wrote:
UNION is not broken; the syntax in the given comment is incorrect. You can
do
SELECT * FROM table UNION SELECT * FROM table
or
(SELECT * FROM table) UNION (SELECT * FROM table)
but not
SELECT * FROM table UNION (SELECT * FROM table)
On 8/4/05, Mike Johnson [EMAIL PROTECTED] wrote:
Hi all,
Some sections of the manual seem to indicate that it's better to
create indexes after data population, rather than before. See section
7.2.14, Speed of INSERT Statements. The general procedure there is
to load the data using LOAD DATA INFILE, and then use myisamchk. This
creates the index tree
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