I have two tables within the same database.
On one I can use the MySQL function LIKE to locate a company name. On the other I always get returned zero results, even when I use a simple match like:
SELECT name
FROM table
WHERE name LIKE 'a%'
Is there a reason for this? Is there a setting or something that needs to be changed?
You could try seeing if you get anything by simply using
SELECT name FROM table WHERE name LIKE '%'
Maybe nothing starts with a?
Please provide an example of the table population and MySQL output. Perhaps you really don't have any names that start with 'a'.
Related
I have a table called blacklisted_usernames. These are usernames with wildcards in them that aren't allowed to be registered onto my site.
create table blacklisted_usernames (
name varchar(64) not null
);
Some dummy data:
insert into blacklisted_usernames (name) values
('%admin%'),
('king%'),
('bad'),
('%cool');
The % indicates the same thing as the wildcard in the LIKE function in MySQL. I want to create an efficient case insensitive query which tells me if a username is blacklisted or not. For example is the username AdminJohn allowed? The answer would be no, because of %admin% being in the blacklisted_usernames table.
I understand I can do something like
SELECT 1
WHERE 'AdminJohn' LIKE '%admin%'
or 'AdminJohn' LIKE 'king%'
or 'AdminJohn' LIKE 'bad'
or 'AdminJohn' LIKE '%cool'
But I am manually typing out all the LIKE's. I also don't think it would be efficient if I created a loop checking it 1 by 1. Is there a way I can make this into an automatic but efficient way of checking against the names in blacklisted_usernames table and determining if a username is allowed?
select 1 from blacklisted_usernames where 'AdminJohn' like name limit 1
Another approach is to use a REGEXP to test them all in a single test:
WHERE 'AdminJohn' REGEXP 'admin|^king|^bad$|cool$'
(Note how the wildcards go away on some and "anchors" are needed on the others.)
Probably this is faster than the original OR+LIKEs or the JOIN+LIKEs. When checking one name REGEXP will be plenty fast (no table scan).
If you need to check all existing names against the blacklisted patterns
SELECT usernames.name,
blacklisted_usernames.name blacklisted_pattern
FROM usernames
JOIN blacklisted_usernames
ON usernames.name LIKE blacklisted_usernames.name
Pay attention - this is complete tablescan, the indices won't be used, so the query will be slow.
You may need to check all existing names against newly added/altered patterns - in this case add according WHERE by blacklisted_usernames table (for example, by created_at or updated_at column).
If you need to check currently created username against all patterns then use the solution provided by ysth.
My current MySql wild card is LIKE '%A%B%'. This can return values that contain A and B.
Can anyone suggest how can I alter the wildcard statement to return values that contain either A or B.
Thanks in advance.
You can add as many like operator you want within the parenthesis with OR condition like below
select * from tablename where (column_name like '%test%' or same_column_name like '%test1%' or
same_column_name like '%test2%' or same_column_name like '%test3%')
For more info have a look at the below link.
SQL Server using wildcard within IN
Hope that helps you
You can use REGEXP
select * from Table1 where some_column REGEXP '[AB]'
there are lots of different ways in writing this as a regular expression, the above basically means containing A or B.
Generally you want to avoid using REGEXP and LIKE '%something' because the do not use indexes. Thus for large tables these operations would be unusable. When you want to do a search of this kind it's always best to stop and ask: "Have I got the best database design?", "Can I use full text search instead?"
Hey guys am really new to mysql.I have heard of alias in mysql and i have tried double alias with the string like
select ('name' as bae,'age' as ages) as person;
When i run the above code it doesnt give me the output and raises the error.I dont understand why the double alias didnt works in mysql.
Any help to make this one correct would be really appreciated..Thanx in advance
The problem with your query are the parentheses. They represent a single expression and you don't put aliases (or commas usually) inside expressions. So, this fixes the immediate problem:
select 'name' as bae, 'age' as ages
I'm not sure what the second "as person" is supposed to be. Perhaps you want a subquery:
select person.*
from (select 'name' as bae, 'age' as ages) person
A really basic MySQL query should look something like:
SELECT
[COLUMN_NAME] AS [ALIAS_NAME]
FROM
[TABLE_NAME]
Based on your query it appears you are trying to retrieve the two columnns name and age from the person table.
If this is the case, the following query can help you:
SELECT
name AS bae,
age AS ages
FROM
person
But, this is still just one big guess, if you really want us to help you with your problems, you should give some more information about what you are trying to achieve.
Ran into a brick wall & I came running here for help.
Is it possible to check if a field is empty in a given mysql table row and no, I do not want to check by each column name ( with a single line sql if possible).
I would elaborate some more:
say if I have a table with columns t1_col1,t1_col2 and ...
so I would like to know if any of these columns is empty.
and if I have another table with columns t2_col1, t2_col2 and ..
I would like to use the SAME sql statement to check if any of these columns are empty.
I have not tried anything, because I do not know what to try, I know it is possible to achieve this by checking if column are null ( if column names are known that is and also I know column names of table can be found by 'show column' of mysql). So those are not the way I want to go. I want to know if there is any single command that can do this checking ?
Can any body help me please.
There is no such thing in MySQL. You will have to check each column.
However, it is possible to get the table schema like this:
DESCRIBE table_name;
It will give you a list of all columns in the table, then using your favorite programming language, you can cycle over all fields to create a query to check if they are empty.
I have a table which includes names and each have a unique itemcode field, however I also have another table which we use as the root table for everything, this extra table is an extra I've recently added.
Because the names in my root table differ from the names in this new table, I need a bridge table, which I've created using a query which performs a INSERT..SELECT where the name in one table is equal to another. This is great, however it's limited my results because some names include The or A at the beginning so I'm missing them. So now I've changed my a = b query to a SOUNDS LIKE however that's only included names with differences at the end.
What I'm looking for is a way of ignoring a certain set of words such as:
The
A
Be
And
Etc and use the rest of the name? I can't do a 'LIKE %%' because that would capture too much.
You can remove the words The, A, Be etc by using the like statement. Ensure you have spaces on either side of the search terms so that it matches whole words, and not partial words.
SELECT * FROM namestable where names Like '% The %'