searching around trying to find a way to add index on suffix of a column I couldn't find a solution.
The only thing for partial index which I found is on prefix of index which is:
CREATE INDEX part_of_name ON customer (name(10));
from 12.1.13. CREATE INDEX Syntax
I also tried other stuff like:
CREATE INDEX part_of_name ON customer (name(-10));
CREATE INDEX part_of_name ON customer (RIGHT(name,10));
CREATE INDEX part_of_name ON customer (SUBSTRING(name,-10));
ALL with same error:
ERROR 1064 (42000): You have an error in your SQL syntax;
I would like your help!
Thank you in advance!
MySQL doesn't support indexes on arbitrary expressions. The prefix index is only a quirk, since it's "free" in a typical implementation of B-Tree indexes.
You'll need to add another column to the table, populate it with a trigger, and put index on that.
Related
Currently I have a MYSQL query that's under performing. I need to create an index on two fields within my query: cancel and complete.
What is the best way to perform this?
SELECT* FROM table WHERE cancel != 'CANCEL' AND complete IN ('COMPLETE','TAKEN_BACK')
To create a multi-column index, but the column names in parentheses.
ALTER TABLE table
ADD INDEX (cancel, complete);
This is equivalent to
CREATE INDEX table_cancel_complete_ix
ON table (cancel, complete);
CREATE INDEX requires you to give a name to the index, it's optional with ALTER TABLE (it will be assigned a default name).
To add an index over more than one column (aka multi-column index or composite index), use this syntax:
ALTER TABLE your_table
ADD INDEX (cancel, complete);
However, you might want to make sure this is the reason for your statement to be underperforming. Take a look into the manual to dig deeper into this.
When I try do next
mysql> CREATE TABLE '20181020';
sql return an error:
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual
that corresponds to your MariaDB server version for the right syntax to use
near ''20181020'' at line 1
How can I solve it?
You needt to wrap identifier with backticks:
CREATE TABLE `20181020`(id INT);
I propose not to do so and use proper meaningful naming. Using date as name of table suggest that it could be table-per-date antipattern.
Related article: SELECT * FROM sales + #yymm
your can also use double quote for this type of table name
CREATE TABLE "20181020" (id INT);
insert into "20181020" values(1)
But this type of naming is not standard practice
The other answers cover the solution, which is to use backticks.
Let me add that using non-standard identifiers is a bad idea. If you start naming columns as number as well, who wants to figure out the differences between 20181020.1, 20181020.1, and 20181020.1. Is it so hard to use a prefix: t_20181020?
But you don't want to do that either. Let me explain. Presumably, if you have one table called 20181020, then tomorrow you will want another table 20181021. This is a really bad database design.
You should be putting all the data into a single table, with a date column specifying the date. You can then run queries over one table to see changes over time -- for instance.
If the tables are large and you want the ability to manipulate each day separately, then you use table partitioning to store each day's worth separately. This is handy, because partitions can be archived, restored, and dropped independently of other partitions.
Hopefully a very quick question: I'm having some trouble getting the following
index creation statement to work. I'm using MySQL Workbench.
CREATE INDEX HIRE_DATE_INDEX
ON Employee (hiredate)
WHERE hiredate > '2001-01-01';
I'm trying to get the following index creation to work, however regardless of what I look up online the following is listed as the proper syntax but for some reason that is unfathomable at this point, the index is specifically saying that the where clause is in the incorrect place.
I'm clearly missing something in the examples.
(Context, just trying to create a filtered index only interested in dates greater then).
It looks like this should be easy as hell, what am I missing here?
You don't need the WHERE clause. But MySQL doesn't support filtered index. (Reference here)
CREATE INDEX HIRE_DATE_INDEX
ON Employee (hiredate);
Also that command doesn't work if you try to create a primary key. If that's the case, you need to use ALTER TABLE command.
From the docs:
An ALTER TABLE statement that contains DROP INDEX and ADD INDEX
clauses that both name the same index uses a table copy, not Fast
Index Creation.
This is a bit unclear to me. Is it talking about the NAME of the index? Can someone give an example of a query in which MySQL resorts to a table copy?
Indeed, it sounds like this line is about:
An (One, single) ALTER TABLE statement
that contains (both) a DROP INDEX and an ADD INDEX clause
and both clauses name the same index
and states that such a statement uses a table copy, not Fast Index Creation.
Such a statement would be:
ALTER TABLE MyTable
DROP INDEX MyIndex
ADD INDEX MyIndex(MyColumn);
The documentation is not really clear about the reason behind this, but I think the database want to create an index first and then drop the other index, so the statement by itself can more easily be made atomic. (Creating the index might fail.) If the index name itself is used in the storage as well, that order of first creating then dropping would give a conflict.
After all, fast index creation is a relatively new feature, so they might improve this over time.
I have a table with spatial column(data type geometry) and with around 450k rows. When i tried to add a spatial index on this column, it returns an error as "All parts of a SPATIAL index must be NOT NULL".
The query to create index is
create spatial index spatIdx on table_name(ogc_geom)
1. Am I doing something wrong?
2. Where these NULL parts came from?
3. If its in my spat data how can i remove it (i tried with is null).
In the MySQL documentation, it states, "Currently, columns in spatial indexes must be declared NOT NULL". My guess is the column ogc_geom is allowed to have NULL. Try:
ALTER TABLE table_name MODIFY COLUMN ogc_geom .... NOT NULL
Any column you create a spatial index on must be defined with "NOT NULL", or else you will get an error.
how about if you use the "ALTER TABLE" statement instead to update your table structure and add the index into it.
try to check the sysntax from this link: http://dev.mysql.com/doc/refman/5.5/en/alter-table.html