I have 2 tables: roles and roles_backup.
due to faulty backend code, values from the field role have been set to NULL (only with certain records).
what i need to acomplish: finding all records from the backup table where role is set in order to get them back.
what is the best method of querying this?
i've tried the following but it doesn't seem to work:
SELECT * FROM roles WHERE (role IS NULL OR role='') UNION
SELECT * FROM roles_backup WHERE (role <>'')
Assuming these records have an ID, you could do something like this to restore your roles from the roles_backup table:
UPDATE roles
SET role = ( SELECT role FROM roles_backup WHERE id = roles.id )
WHERE role IS NULL
Related
Scenario is like this:
list of different types of insurance [ID, name, desc]
each insurance has a different unique table. [ID, user_id, ]
I want to query to show the columns of Insurance like [ID, Name, DESC] and a new column to show whether this user has applied for this insurance or not. No need to worry for the user part.
Just guide me how can I sub-query with dynamic table name.
I tried making a setup table where each insurance maps to its table name. But in my sub query how to do that.
If user has applied then show 1 otherwise 0.
SELECT i1.ID,
i1.name,
i1.desc,
IF(true, 1, 0) AS EXIST
#(SELECT t1.c_user_id FROM #tbl_name t1 WHERE t1.id = '101')
FROM app_fd_pdrm_insur_type i1;
Please, guide me what to replace with true.
Thank you.
Try this:
SELECT i1.ID, i1.name, i1.desc, IF( EXISTS(SELECT t1.c_user_id FROM #tbl_name t1 WHERE t1.id = '101'), 1, 0) as Exists FROM app_fd_pdrm_insur_type i1;
what if I have two strings: "123" and "abc". I want to select username if there's username "123" then choose it, if not found (null) then select username where "abc"
I have a table called USERS, this table responsibility with workflow engine account. I want to show columns in USERS:
username
email
usr_firstname
usr_lastname
I am using concat to merge column 3 and 4 with space between it. In the office, there are 2 types of employee:
origin/internal employee
outsource/partner employee
Origin employee login into every system using LDAP (FirstName.LastName), but outsource or partner employee login individually just for our workflow engine using employee identity number.
In this case, if I use something like:
Where username = 'employeenumber' or username = 'LDAPacc' the result is both account (used and unused for outsource) they appear. I want to show just 1 rows and 1 query but it's work with internal or even outsource (they will got data correctly for outsource).
You can use like this query;
SELECT *
FROM TABLE
WHERE username IN ('123', 'abc')
AND (username='123' OR NOT EXISTS(SELECT * FROM TABLE WHERE username='abc'))
You could use COALESCE.
COALESCE selects the first non null value out of the ones supplied.
So you could use....
SELECT COALESCE(String_123, string_ABC);
If string_123 has a value it will select that, otherwise it will select string_ABC unless of course they are both null.
So to be safe include a default value.......
SELECT COALESCE(String_123, string_ABC, string_Default);
I've found when I tested my logic to mysql tryit editor by w3schools and It's worked properly what I need. Here's my query:
SELECT * FROM Customers WHERE CustomerID = 'zz' OR (NOT EXISTS (SELECT * FROM Customers WHERE CustomerID = 'zz') AND CustomerID = '3')
let's say CustomerID is equivalent to my username column, then I tried to swap 'zz' and '3' value and it's still works. I hope there's more simple query than this
I have a table (pdt_1) in database (db_1) and another table (pdt_2) in another database (db_2).
I met pdt_1 and pdt_2 to find pdt_1 products not present and published in pdt_2.
functional code :
SELECT * FROM db_1.pdt_1 AS lm
WHERE lm.product_sku
NOT IN (SELECT DISTINCT product_cip7 FROM db_2.pdt_2)
AND lm.product_publish=‘Y'
finally, I need to insert the result of this query in pdt_2.
However, the structure of pdt_1 and pdt_2 are different.
Example:
- columns's names
- columns's numbers
I also need an auto_increment id for pdt_1 products inserted into pdt_2.
I need help.
NB : sorry for my poor english :(
If you want a new table with just the id and product_sku, try:
INSERT INTO new_table # with id and product_sku from first table
SELECT pdt_1.id,
pdt_1.product_sku
FROM db_1.pdt_1
LEFT JOIN db_2.pdt_2
ON pdt_1.product_sku = pdt_2.product_cip7
WHERE pdt_2.product_cip7 IS NULL
AND pdt_1.product_publish = 'Y'
I have a simple user preferences table that looks like this:
id | user_id | preference_name | preference_value
What makes this table unique though is if the user_id field is null, it means it is the default value for that preference. I'm trying to get all the preferences for a user and use the default value only if an actual value hasn't been specified for that user.
So basically I need to:
SELECT * FROM user_preferences WHERE user_id = {userIdVar} OR user_id IS NULL;
BUT, I want to throw out a user_id is null result if there is another row in the result set with the same preference_name and a value for user_id.
Is there a way to do this with a single SQL query or should I do this in code?
Use NOT EXISTS:
SELECT up1.*
FROM user_preferences up1
WHERE ( NOT EXISTS(SELECT 1
FROM user_preferences up2
WHERE user_id = {userIdVar})
AND user_id IS NULL )
OR ( user_id = {userIdVar} );
There are various ways you can do this, but if all preferences have a default value, or you have a complete list of preferences somewhere else, I would do it like this:
select
default_preferences.preference_name,
coalesce(
real_user_preferences.preference_value,
default_preferences.preference_value) as preference_value
from
(select * from user_preferences where user_id is null)
as default_preferences
left join
(select * from user_preferences where user_id = #user_id)
as real_user_preferences
on
real_user_preferences.preference_name = default_preferences.preference_name
You've tagged your question both MySQL and SQL Server, I don't know which dialect you're looking for. I know SQL Server accepts this syntax, but it might need some tweaking for MySQL.
Edit: funkwurm points out that subqueries make this likely to perform poorly on MySQL. If that turns out to be a problem, it can be rewritten without subqueries as
select
default_preferences.preference_name,
coalesce(
real_user_preferences.preference_value,
default_preferences.preference_value) as preference_value
from
user_preferences as default_preferences
left join
user_preferences as real_user_preferences
on
real_user_preferences.preference_name = default_preferences.preference_name
and real_user_preferences.user_id = #user_id
where
default_preferences.user_id is null
Edit 2: if there are preferences that do not have a default value, the first version can be modified to use full join instead of left join, and take preference_name from either the defaults or the user-specific preferences, just like preference_value. However, the second version is not so easily modified.
COALESCE returns the first non null values of the params provided: http://dev.mysql.com/doc/refman/5.0/en/comparison-operators.html#function_coalesce
So if you grab the set of default preferences and JOIN them with the users preferences, you can use the COALESCE in your columns to populate the correct values.
This should work to select the first row that is either NULL or set the the user_id variable where the user_id variable is preffered if both are set and then shows every preference_name only once.
SELECT
*
FROM
(
SELECT
*
FROM
user_preferences
WHERE
user_id = {userIdVar} OR
user_id IS NULL
ORDER BY
CASE WHEN user_id IS NULL THEN 1 ELSE 0 END
) sub_query
GROUP BY
preference_name
SQL FIDDLE
I have the task to repair some invalid data in a mysql-database. In one table there are people with a missing date, which should be filled from a second table, if there is a corresponding entry.
TablePeople: ID, MissingDate, ...
TableEvent: ID, people_id, replacementDate, ...
Update TablePeople
set missingdate = (select replacementDate
from TableEvent
where people_id = TablePeople.ID)
where missingdate is null
and (select count(*)
from TableEvent
where people_id = TablePeople.ID) > 0
Certainly doesn't work. Is there any other way with SQL? Or how can I process single rows in mysql to get it done?
We need details about what's not working, but I think you only need to use:
UPDATE TablePeople
SET missingdate = (SELECT MAX(te.replacementDate)
FROM TABLEEVENT te
WHERE te.people_id = TablePeople.id)
WHERE missingdate IS NULL
Notes
MAX is being used to return the latest replacementdate, out of fear of risk that you're getting multiple values from the subquery
If there's no supporting record in TABLEEVENT, it will return null so there's no change