order result of query by on of two columns - sql

I have this table:
CREATE TABLE Foo
(
id_key INTEGER PRIMARY KEY,
key1 INTEGER NOT NULL,
seq_num1 INTEGER NOT NULL,
key2 INTEGER,
seq_num2 INTEGER,
data BLOB NOT NULL
);
And I want to select data where key1 or key2 match,
this is simple:
SELECT data
FROM Foo
WHERE (key1 = ? OR key2 = ?)
but then I want to order results of this query by seq_num1 or seq_num2, depending on what matched in the table's row - key1 or key2 respectively.
I think that something like this should work:
SELECT data
FROM Foo
WHERE (key1 = ? OR key2 = ?)
ORDER BY
CASE
WHEN key1 = ?
THEN seq_num1
ELSE seq_num2
END
but I'm not sure is this optimal solution? Because of in this query I compare key1 twice, while it should be enough compare once.
I use sqlite3.


Could this be what you want? I don't use sqlite, but this mysql command seems to be understood by sqlite.
select
data, seq_num1 as seq
from Foo
where key1 = ?
union
select
data, seq_num2 as seq
from Foo
where key2 = ?
order by seq;

Related

Rename category in the column in SQL Server

Here is the query
select col1
from table
col1 contains these category values:
A
B
C
NULL
How can I rename null category to D?

If you want to make the change permanent
UPDATE table
SET col1 = 'D'
WHERE col1 IS NULL
From then on you can simply query with ...
SELECT col1
FROM table
... to get the desired result.
If there is more than one row having a NULL in col1, you need to filter by a unique key, preferably by the primary key (which every table should have by the way). Let's say you have a table like
id (PK) col1
--- ----
1 'A'
2 'B'
3 'C'
4 NULL
5 NULL
then you can fix it with
UPDATE table SET col1 = 'D' WHERE id = 4;
UPDATE table SET col1 = 'E' WHERE id = 5;
unless you can calculate the new value from another column, e.g.:
UPDATE table
SET col1 = UPPER(LEFT(name, 1))

Try this : ISNULL( ) function is used to replace NULL value with another value
select isnull(col1,'D') as col1
from table

SQL Server uses ISNULL().
SELECT ISNULL(value_to_check, use_this_instead_if_valuetocheck_is_null)
For your code:
select ISNULL(col1, 'D') AS col_name
from table
However, this will happen across the board for this column. You can't use this to make a sequence, like D then E then F. Any NULL value you come across in this column will change to D.

insert select alias value into column

Not sure if this is the best title, but i want to select string values into an int column of a new table (the reason is to use keys with int data types rather than strings, so there are more columns not shown in this example)
table1.key1 table2.key2
a 1
b 2
c 3
a 1
one way i can do this is as follows but the syntax is very very long in some scenarios
insert into table2 (key2)
select 1
from table1
where key1 = 'a'
insert into table2 (key2)
select 2
from table1
where key1 ='b'
etc...
can someone show me how i could use a syntax that is shorter? also i have to keep identity insert set to off so an update statement will not work from what i understand.

SQL Fiddle Demo
Use a CASE expresion
insert into table2 (key2)
select CASE WHEN key1 = 'a' THEN 1
WHEN key1 = 'b' THEN 2
WHEN key1 = 'c' THEN 3
.....
ELSE -1
END as key2
from table1

Select where column in not null array

I am trying to do :
SELECT *
FROM table
WHERE column IN (SELECT col FROM table2 WHERE col2 = value )
but I want to check if the second request doesn't return a null array.
How is that possible?
Thanks in advance

Simply add a NOT NULL check in the subquery to omit the null values returned.
SELECT * FROM table WHERE column IN
(SELECT col FROM table2 WHERE col2 = value AND col IS NOT NULL);

Sql: How to properly check if a record exists that matches 3 column

I have read through the forum but i could not find any example or answer for check existing record for multiple column.
Question:
To check if an entry exist if match 3 column. There is 9 column in the table if 2 column entry match are not counted as existing record.

SELECT COUNT(id) AS existing_row_count FROM tablename WHERE col1 = ? AND col2 = ? AND col3 = ?
If existing_row_count returns greater than zero then we can say that there is at least one match. You can try this also:
SELECT id FROM tablename WHERE col1 = ? AND col2 = ? AND col3 = ?
Thus, you can get the matching row id numbers. And if we combine those two queries:
SELECT id, COUNT(id) AS existing_row_count FROM tablename WHERE col1 = ? AND col2 = ? AND col3 = ?

SQL query grouped parameter maximum

Let's say I had two columns in a database, col1 and col2. Column 2 is the time, Column 1 something. In my query, I want to do the following:
I want to SELECT * from my table and group the results by col1. However, I only want those entries where for the grouped col1 there is no value of col2 higher than a certain value. Meaning that, I only want those col1-s for which col2 does not exceed a certain value.
If, for instance, I had three rows, as follows:
ROW1: col1 = val1, col2 = 3
ROW2: col1 = val1, col2 = 5
ROW3: col1 = val2, col2 = 3
ROW4: col1 = val2, col2 = 4
And I do not want the time for any of them to exceed 4, then, as a result, I would only want ROW3 or ROW4, which, does not matter, for col1 is the same and is grouped. But in rows 1 and 2, that are grouped by col1's value "val1", in one of them col2 DOES exceed 4, therefore, I do not want any of them.

SELECT col1 FROM table GROUP BY col1 HAVING MAX(col2) <= 4
Because you want only the common value (col1) from the group, you can use GROUP BY. When you do a GROUP BY (aggregate) query, you can use the HAVING clause to apply a filter to the aggregated data set.

I am not use I got the point (my english is not good).
I think sub-query is the best choice.
Note: this example should work with mySql ...
SELECT *
FROM table
WHERE col1 IN
(SELECT col1 FROM table WHERE col2 < 5 GROUP BY col1)
ORDER BY col1

CREATE TABLE x (
t TIME NOT NULL,
v INT NOT NULL );
INSERT INTO x VALUES
('13:14:00', 24),
('13:14:00', 27),
('13:14:00', 29),
('17:12:00', 14),
('17:12:00', 20),
('17:12:00', 24);
SELECT t, MAX(v) AS mv FROM x
GROUP BY t
HAVING mv <= 25;
Or do I misunderstand the question?