Get unique values of a field and prints its length - mysql

Table Name: Worker,
Fields : worker_id | first_name | last_name | department
I have a table name worker and i wanted to write an SQL query that fetches the unique values of DEPARTMENT from Worker table and prints its length. So i tried running this : (Database- Mysql)
select length(distinct(department)) from worker;
But it is giving an error saying:
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'distinct(department)) from worker' at line 1
But when i ran below query, it works perfectly fine:
select distinct(length(department)) from worker;
Can somebody please explain me why interchanging distinct and length function makes query works?
Thanks in advance!


Try not to use distinct like function but clause otherwise it will give syntax error.
Below sql statement will execute as shown below:
select distinct (length('xyz')) ---- length('xyz') : 3
select distinct (3) ---- output : 3


Distinct is not properly a function but a clause
select distinct length(department) from worker;
Anyway in MySQL work also with function syntax
select distinct( length(department)) from worker;
The code with the exchanged token don't work because DISTINCT produce an aggregated result removing the duplicated values,this implies that the outer length() function work on not correct set of rows or better the db engine see that there an improper use of the DISTINCT clause and raise the syntax error
select length( distinct 'A' ) this raise an error
If you want use the outer length() function you should code this way
select length(my_col) from (
select distinct department my_col from worker
) ;


correct answer :
select distinct <column_dept> as department***,*** (len(<column_dept>) as length_column_dept from xyz_table


select distinct( length(department)),department from worker group by department;


select distinct (Department) as 'Unique department', len(Department) as 'length of name' from Worker;

Related

I have a issue with the if statement in mysql

I want to execute a if statement which is like this
select IF ( quantity_wanted!=3,(select name from grocerywanted),Null) AS message from grocerywanted;
I want here to check the quantity_wanted column if it contains a value except 3 run the select statement

Your query is using same table name not as sub query. I think you should use 'name' in replace of '(select name from grocerywanted)'. You will get your desired output.
select IF ( quantity_wanted!=3,name,Null) AS message from grocerywanted;

Totals and Runningtotals with SQL "sum" and "over" Syntax

In my SQL table I have "country" and "we200326" columns. Column "we200326" contains only "1" or "NULL" entries.
I'm trying to get a total of all "1"s in column "we200326" and a total by country. I have written the following statement but it gives an error but I don't know what I did wrong (I'm very new at this):
SELECT country, we200326,
(SUM(we200326) OVER () AS Total)
(SUM(we200326) OVER (PARTITION BY country) AS CountryTotal)
FROM table_name
ORDER BY CountryTotal, Country;
The error I get is this:
MySQL said: Documentation
#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'OVER () AS Total)
(SUM(we200326) OVER (PARTITION BY country) AS CountryTotal)
' at line 2
I have searched for similar errors and found several (each time was a simple syntax error like a space or comma or so) I tried several versions but could not resolve my problem when following those instructions. Any help would be appreciated.

Window functions are available in MySQL 8.0 only.
In earlier versions, one option is to use subqueries:
select
country,
wewe200326,
(select sum(we200326) from table_name) total,
(select sum(we200326) from table_name t1 where t1.country = t.country) country_total
from table_name t
order by country_total, country

How to use multiple SELECT statement in INSERT statement and also in CONCAT() function

I'm working on a project where i want to insert data from another table and also use select statement in concatenate function but i can't understand ?
INSERT INTO c_order
(oid,cid,servicename,servicetype,servicecategory,price,address,date,status,time)
VALUES
('qw121','121',(select servicename,servicetype,price, from inner_subservice where inssid=1),(select building,city,pincode CONCAT(building,'',city,'',pincode) as fullname from address where cid='121',now(),'ongoing',null);
1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'from inner_subservice where inssid=1),(select building,city,pincode CONCAT(build' at line 1

INSERT INTO c_order(oid,cid,servicename,servicetype,servicecategory,price,address,date,status,time)
VALUES("qw121","121",
(select servicename,servicetype,price from inner_subservice where inssid=1),
(select building,city,pincode, CONCAT(building,'',city,'',pincode) as fullname from address where cid='121'),now(),
'ongoing',null);
You were missing some parenthesis and you had some extra comas there. Apart from those this query should work fine.

INSERT INTO c_order(oid,cid,servicename,servicetype,servicecategory,price,address,date,status,time) VALUES("qw121","121",(select servicename,servicetype,servicecategory,price from inner_subservice where inssid=1),(select CONCAT(building,'',city,'',pincode) as fullname from address where cid='121'),now(),'ongoing',null);
Couldn't comment on pr1nc3's answer because i don't have enough rep, but his query needed a small tweak and hopefully this would work.
Instead of selecting building, city and pincode from address you only need to select the concat() result of the respective fields. Also you didn't select servicecategory field.

MySQL: Ordering of columns when using a wildcard with group by has odd behavior

What is the difference between these two MySQL statements?
Works:
select *, count(mycol) c from mytable group by mycol;
Doesn't work:
select count(mycol) c, * from mytable group by mycol;
The first statement works as I'd expect, while the second one gives me a syntax error. Why does the order matter?
I'm having trouble finding an answer from Google, because I'm not entirely sure if I'm asking the question correctly.
Edit:
Here's the sanitized error message. I'm using MySQL Workbench, if that's relevant.
Error Code: 1064. You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '* from mytable group by id' at line 1

Just alias the table and the syntax error will go away.
select count(t.id) c, t.* from mytable t group by id;
See this db fiddle.
It looks like MySQL allows bare (unqualified) * only as immediatly following SELECT. The following query also raises a syntax error :
select 1, * from mytable t;
The documentation prevents against using bare * combined with other items in the SELECT list :
A select list consisting only of a single unqualified * can be used as shorthand to select all columns from all tables.
Use of an unqualified * with other items in the select list may produce a parse error. To avoid this problem, use a qualified tbl_name.* reference.

Wrapping SQL query in parentheses causes syntax error

The following query works:
SELECT DISTINCT `number`
FROM `employee`
WHERE `number` IN
(SELECT `department_manager`
FROM `department`)
UNION
(SELECT DISTINCT `manager`
FROM `employee`
WHERE `manager` IS NOT NULL)
But as soon as I wrap the query with parentheses it doesn't work anymore:
(SELECT DISTINCT `number`
FROM `employee`
WHERE `number` IN
(SELECT `department_manager`
FROM `department`)
UNION
(SELECT DISTINCT `manager`
FROM `employee`
WHERE `manager` IS NOT NULL))
Causing syntax error:
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'UNION
Wrapping other select queries in parentheses doesn't cause problems, this works for example:
(SELECT DISTINCT number FROM johnson.employee);
What is the difference between these?

This has to do with the way MySQL implemented its SQL grammar.
A <query> can be:
SELECT ... [ UNION <query>]
or
( SELECT ... ) [ UNION <query> ]
But apparently not
( SELECT ... UNION <query> )
Read sql/sql_yacc.yy in the MySQL source code if you want the details.
As a workaround, you can do this:
SELECT * FROM (SELECT ... UNION SELECT ... ) AS t;

Parentheses around queries are subqueries -- think of this almost like a subroutine, where the inner query is executed first, then its result is evaluated in the context of the outer query. In your second example, you are defining a subquery where no outer query exists, hence a syntax error.
You might be able to transform the second example into valid sql simply by putting a SELECT before the first parenthesis and 'FROM DUMMY' after the closing parenthesis; try it.