Columns:
FirstName
MiddleName
LastName
I want to automatically concatenate into a 4th column called 'FullName' separated by spaces Every time data is entered or changed in one of the above 3 columns the 'FullName' column is updated.
Sample Data
giving a mysql answer since you left a mysql tag:
In MySQL you can create a generated column, using the CONCAT_WS function.
Postgres doesn't support( as of Version 11 ) a Virtual column / derived column.
You may create a View instead.
CREATE OR replace VIEW v_names
AS
SELECT firstname,
middlename,
lastname,
firstname
||CASE
WHEN nullif(middlename, '') IS NULL THEN ''
ELSE ' '
||middlename
END
||CASE
WHEN nullif(lastname, '') IS NULL THEN ''
ELSE ' '
||lastname
END AS FullName
FROM names;
knayak=# INSERT INTO names(FirstName,MiddleName,LastName) VALUES ( 'John', 'Maynard','Keynes');
INSERT 0 1
knayak=# INSERT INTO names(FirstName,MiddleName,LastName) VALUES ( 'John','','Doe');
INSERT 0 1
knayak=# select * from v_names;
firstname | middlename | lastname | fullname
-----------+------------+----------+---------------------
John | Maynard | Keynes | John Maynard Keynes
John | | Doe | John Doe
Related
Here's some sample data
ID | sys1lname | sys2lname
------------------------------------
1 | JOHNSON | JOHNSON
2 | FULTON | ANDERS-FULTON
3 | SMITH | SMITH-DAVIDS
4 | HARRISON | JONES
The goal is to find records where the last names do NOT match, BUT allow when sys1lname can be found somewhere within sys2lname, which may or may not be a hyphenated name. So from the above data, only record 4 should return.
When I put this (SUBSTRING(sys2lname, CHARINDEX(sys2lname, ccm.NAME_LAST), LEN(sys1lname))) in the SELECT statement it will properly return the part of sys2lname that matches sys1lname.
But when I use that in the WHERE clause
WHERE 1=1
AND sys1lname <> sys2lname
OR sys1lname not in ('%' + (SUBSTRING(sys2lname, CHARINDEX(sys1lname, sys2lname), LEN(sys1lname))))
the records with hyphenated names are in the result set.
And I can't figure out why.
Just use a NOT LIKE:
SELECT ID
FROM dbo.YourTable
WHERE sys2lname NOT LIKE '%' + sys1lname + '%';
If you could have a name like 'Smith' in sys1lname and 'BlackSmith' (or even 'Green-Blacksmith') in sys2lname and don't want them to match, I would use STRING_SPLIT and a NOT EXISTS:
SELECT ID
FROM dbo.YourTable YT
WHERE NOT EXISTS (SELECT 1
FROM STRING_SPLIT(YT.sys2lname,'-') SS
WHERE SS.[value] = YT.sys1lname);
Question is not too specific but not sure how to explain the question well.
I have table in my db with names in the field.
I would like to order the names in the way if the name starts with certain alphabet, order that first and so on.
What I have now is
SELECT
(T.firstname||' '||T.lastname) as Full_Name
FROM
TABLE T
ORDER BY
CASE
WHEN LPAD(T.firstname, 1) = 'J' THEN T.firstname
WHEN LPAD(T.firstname, 1) = 'B' THEN T.firstname
END DESC,
Full_Name ASC
Now this returns as what I would like to see, name starting with 'J' is ordered first then 'B' then the rest.
However, the result looks like
What I get What I want
Full_Name Full_Name
---------- ----------
Junior MR James A
John Doe Joe Bob
Joe Bob John Doe
James A Junior MR
Brad T B Test
Bob Joe Bb Test
Bb Test Bob Joe
B Test Brad T
A Test A Test
Aa Test Aa Test
AFLKJASDFJ AFLKJASDFJ
Ann Doe Ann Doe
But what I want is that J and B to be sorted alphabetical order as well, right now it is doing reverse alphabetical order.
How can I specify the order inside of case?
I tried having 2 seperate case statement for different cases for starting with 'J' and 'B', it just shows me the same result
Just make one extra column, material using triggers or volatile using expression only executed when select is run, and then use it in sorting.
For secondary sorting use original components of names, not the expression bringing both names together thus destroying the information which was which.
Examples: https://dbfiddle.uk/?rdbms=firebird_3.0&fiddle=fbf89b3903d3271ae6c55589fd9cfe23
create table T (
firstname varchar(10),
lastname varchar(10),
fullname computed by (
Coalesce(firstname, '-') || ' ' || Coalesce(T.lastname, '-')
),
sorting_helper computed by (
CASE WHEN firstname starting with 'J' then 100
WHEN firstname starting with 'B' then 50
ELSE 0
END
)
)
Notice the important distinction: my helper expression is "ranking" one. It yields one of several pre-defined ranks, thus putting "James" and "Joe" into the same bin having exactly the same ranking value. Your expression still yields the names themselves, thus erroneously keeping difference between those names. But you do NOT want that difference, you told you want all J-started names to be moved upwards and then sorted among themselves by usual rules. So, just do what you say, make an expression that pulls all J-names together WITHOUT making distinction between those.
insert into T
select
'John', 'Doe'
from rdb$database union all select
'James', 'A'
from rdb$database union all select
'Aa ', 'Test'
from rdb$database union all select
'Ann', 'Doe'
from rdb$database union all select
'Bob', 'Joe'
from rdb$database union all select
'Brad', 'Test'
from rdb$database union all select
NULL, 'Smith'
from rdb$database union all select
'Ken', NULL
from rdb$database
8 rows affected
select * from T
FIRSTNAME | LASTNAME | FULLNAME | SORTING_HELPER
:-------- | :------- | :---------- | -------------:
John | Doe | John Doe | 100
James | A | James A | 100
Aa | Test | Aa Test | 0
Ann | Doe | Ann Doe | 0
Bob | Joe | Bob Joe | 50
Brad | Test | Brad Test | 50
null | Smith | - Smith | 0
Ken | null | Ken - | 0
Select FullName from T order by sorting_helper desc, firstname asc, lastname asc
| FULLNAME |
| :---------- |
| James A |
| John Doe |
| Bob Joe |
| Brad Test |
| - Smith |
| Aa Test |
| Ann Doe |
| Ken - |
Or without computed-by column
Select FullName from T order by (CASE WHEN firstname starting with 'J' then 0
WHEN firstname starting with 'B' then 1
ELSE 2
END) asc, firstname asc, lastname asc
| FULLNAME |
| :---------- |
| James A |
| John Doe |
| Bob Joe |
| Brad Test |
| - Smith |
| Aa Test |
| Ann Doe |
| Ken - |
For extra tuning of the positioning of the rows lacking name or surname you can also use NULLS FIRST or NULLS LAST option as described in Firebird docs at https://firebirdsql.org/file/documentation/reference_manuals/user_manuals/html/nullguide-sorts.html
The problem with this approach however, on big enough tables, would be that you won't be able to use indices built over names and surnames for sorting, instead you would have to resort to un-sorted pulling of data (aka NATURAL SORT when reading QUERY PLAN) and then sorting it into temporary files on disk. Which might turn very slow and volume-consuming on large enough data.
You can try to make it better by creating "index by the expression", using your ranking expression there. And hope that FB optimizer will use it (it is quite tricky with verbose expressions like CASE). Frankly you would probably still be left without it (at least I did not manage to make FB 2.1 utilize index-by-case-expression there).
You can "materialize" the ranking expression into a regular SmallInt Not Null column instead of COMPUTED BY one, and use TRIGGER of BEFORE UPDATE OR INSERT type keep that column populated with proper data. Then you can create a regular index over that regular column. While it will add two bytes to each row, that is not that much a grow.
But even then, the index with very few distinct values does not add much value, it will have "low selectivity". Also, index-by-expression can not be compound one (meaning, including other columns past the expression).
So for large data you'd practically better be with using THREE different queries fused together. Add scaffolding, if you did not do already:
create index i58647579_names on T58647579 ( firstname, lastname )
Then you can do triple-select like this:
WITH S1 as (
select FullName from T58647579
where firstname starting with 'J'
order by firstname asc, lastname asc
), S2 as (
select FullName from T58647579
where firstname starting with 'B'
order by firstname asc, lastname asc
), S3 as (
select FullName from T58647579
where (firstname is null)
or ( (firstname not starting with 'J')
and (firstname not starting with 'B')
)
order by firstname asc, lastname asc
)
SELECT * FROM S1
UNION ALL
SELECT * FROM S2
UNION ALL
SELECT * FROM S3
And while you would traverse the table thrice - you would do it by pre-sorted index:
PLAN (S1 T58647579 ORDER I58647579_NAMES INDEX (I58647579_NAMES))
PLAN (S2 T58647579 ORDER I58647579_NAMES INDEX (I58647579_NAMES))
PLAN (S3 T58647579 ORDER I58647579_NAMES)
I have 2 tables consider table named as fp and batch, I have to join 2 tables based on fp[primary key] of 1st table and fp_inst_id from 2nd table such that my output is :
First table all columns and 2nd table one column which is concatenated string of all the rows from join of table 1 and table 2 on fp.id and batch.fp_inst_id.
Note :
[there will be multiple fp_inst_id(of table 2) for unique ID(of table 1)]
Let me give you an example :
Created tables :
CREATE TABLE fp (
PersonID int,
LastName varchar(255),
FirstName varchar(255),
Address varchar(255),
City varchar(255)
);
CREATE TABLE batch (
batchID int,
fp_inst_id int,
xyz varchar(255),
abc varchar(255)
);
insert into fp values(1,'savan','nahar','abc','xyz');
insert into fp values(2,'mmm','asmd','aawd','12k3mn');
insert into batch values(1,1,'garbage1', 'abc1');
insert into batch values(2,1,'garbage2', 'abc2');
insert into batch values(3,1,'garbage3', 'abc3');
insert into batch values(4,2,'garbage9', 'abc9');
If i do normal join like this :
select * from fp join batch on fp.PersonID = batch.fp_inst_id;
What I want is :
Batch columns can be different like it's ok if it has some other delimiter of not surrounded by [] and separated on ';' or something.
What I have tried:
The same thing can be done using MYSQL using STUFF, FOR XML PATH
But it seems to be difficult in POSTGRES SQL as it doesn't support these things,
In POSTGRES SQL I tried string_agg, but it says me to group by everything
2nd thing I was trying was :
Using with clause first create the concatenated strings of table 2 group by on fp_inst_id, but in POSTGRES SQL, it allows group by on primary key(which is normal select) or it asks to use the aggregate function
I'm trying to do this in POSTGRES SQL through a query.
Thanks for the help in advance
Use array_agg to combine the batch rows and group-by to bracket the combination.
select personid,lastname,firstname,address,city,
array_agg(batch)
from fp
join batch on fp.PersonID = batch.fp_inst_id
group by personid,lastname,firstname,address,city;
eg:
jasen=# select personid,lastname,firstname,address,city,array_agg(batch) from fp join batch on fp.PersonID = batch.fp_inst_id group by 1,2,3,4,5;
personid | lastname | firstname | address | city | array_agg
----------+----------+-----------+---------+--------+---------------------------------------------------------------------
2 | mmm | asmd | aawd | 12k3mn | {"(4,2,garbage9,abc9)"}
1 | savan | nahar | abc | xyz | {"(1,1,garbage1,abc1)","(2,1,garbage2,abc2)","(3,1,garbage3,abc3)"}
here the batch column technically contains an array of tuples, but the sting representation seems acceptable.
Alternatively you can use concat_ws() to concat the values and then group by
select personid,lastname,firstname, address,city, array_agg(batch_columns) as batch_columns
from
(select fp.*, concat_ws(' / ',batch.batchid,batch.fp_inst_id, batch.xyz,batch.abc)::text as batch_columns
from fp
join batch
on fp.personid=batch.fp_inst_id)as table1
group by 1,2,3,4,5;
personid | lastname | firstname | address | city | batch_columns
----------+----------+-----------+---------+--------+---------------------------------------------------------------------------------
1 | savan | nahar | abc | xyz | {"1 / 1 / garbage1 / abc1","2 / 1 / garbage2 / abc2","3 / 1 / garbage3 / abc3"}
2 | mmm | asmd | aawd | 12k3mn | {"4 / 2 / garbage9 / abc9"}
I got a key-value based table where each key-value pair is assigned to an entity which is identified by an id:
|_id__|_key_______|_value_|
| 123 | FIRSTNAME | John |
| 123 | LASTNAME | Doe |
And I want to transform it a structre like this:
|_id__|_firstName_|_lastName_|
| 123 | John | Doe |
I suppose one can use postgres build in crosstab function to do it.
Can you show me how to do it and explain why it works?
First of all activate the build in tablefunc-extension:
CREATE EXTENSION tablefunc;
Then create table and add sample data:
CREATE TABLE example (
id int,
key text,
value text
);
INSERT INTO example VALUES
(123, 'firstName', 'John'),
(123, 'lastName', 'Doe');
Now lets prepare the crosstab statment:
SELECT *
FROM example
ORDER BY id ASC, key ASC;
Its important to have the ORDER BY here.
Result:
|_id__|_key_______|_value_|
| 123 | FIRSTNAME | John |
| 123 | LASTNAME | Doe |
Solution
Now crosstab creates the table as we want:
SELECT *
FROM crosstab(
'SELECT *
FROM example
ORDER BY id ASC, key ASC;'
) AS ct(id INT, firstname TEXT, lastname TEXT);
Result:
|_id__|_firstName_|_lastName_|
| 123 | John | Doe |
How it works #1
To however understand how it works I found it easiest to just change the ORDER BY and see what happens:
SELECT *
FROM crosstab(
'SELECT *
FROM example
ORDER BY id ASC, key DESC;'
) AS ct(id INT, firstname TEXT, lastname TEXT);
Result:
|_id__|_firstName_|_lastName_|
| 123 | Doe | John |
As we changed the sorting of the key, the crosstab function sees the keys sorted in the other direction, thus reversing the generated columns.
How it works #2
Another thing that helped me understand how it works: the column definition is all about positions:
SELECT *
FROM crosstab(
'SELECT *
FROM example
ORDER BY id ASC, key ASC;'
) AS ct(blablafirst INT, blablasecond TEXT, blablathird TEXT);
Result
|_blablafirst__|_blablasecond_|_blablathird_|
| 123 | John | Doe |
What is wrong with this query?
SELECT gid, (tex1||' '||tex2) AS ident FROM my_table ;
The structure of my_table is as follow:
gid serial NOT NULL
tex1 CHARACTER VARYING(254)
tex2 CHARACTER VARYING(254)
The content of my_table is:
gid | tex1 | tex2
----+--------+--------
1 | A | dog
2 | Two | birds
3 | More | things
The result of the query is:
gid | ident
----+-------
1 |
2 |
3 |
I would have never thought having troubles with such a simple query...
Thanks for help !
Are you sure that the sample data you are providing is correct?
What is the output of: SELECT gid, (tex1||' '||tex2) IS NULL FROM my_table;?
It seems that either tex1 or tex2 (or both) is NULL, thus the concatenation also produces NULL. Use COALESCE to provide a non null default value to use in such cases.
SELECT
gid,
(COALESCE(tex1, '') || ' ' || COALESCE(tex2, '')) AS ident
FROM
my_table;