We have 2 columns in a table and want to SELECT the lesser most of the two (unless it is equal to 0, then we want the nonzero column).
Is there a way to do this while keeping it a simple SELECT statement?
What we want is this:
SELECT LEAST(col1, col2) FROM myTable
Unless col2 is 0, in which case we want col1.
SELECT LEAST(
IF(col1, col1, col2),
IF(col2, col2, col1)
)
FROM myTable
SELECT
CASE
WHEN col1 = 0 THEN col2
WHEN col2 = 0 THEN col1
ELSE LEAST(col1, col2)
END AS MinCol
FROM myTable
Related
In my MySql database, I want to create select query which should give output like this:
in my select query i want a column output as 1, if the column value present in a list returned by a select query else 0 .
Select col1,col2,
,IF col3 IN
((select col from tabl2 ),1,0)AS col5
from tbl1.
Thanks in Advance
SELECT col1, col2,
IF col3 IN ((select col from tabl2 ),1,0) AS col5
FROM tbl1
Using IF and subquery in MySQL
SELECT table1.column1, table1.column2,
(
SELECT IF (
(SELECT column3 FROM table1 WHERE column3 IN (SELECT column FROM table2)), 1, 0
)
) AS column_output
FROM table1
In general:
SELECT col1,
col2,
CASE WHEN col3 IN (select col from tabl2)
THEN 1
ELSE 0
END AS col5
FROM tbl1
Specific for MySQL:
SELECT col1,
col2,
col3 IN (select col from tabl2) AS col5
FROM tbl1
I understand that LIKE can not be used in inside IN clause from here.
My table has col1, col2, col3 columns.
How can I find multiple values in multiple columns using LIKE operator.
Currently my query is:
SELECT col1, col2, col3
FROM table_name
WHERE
(
Col1 = '38'
OR Col1 LIKE '%,38'
OR Col1 LIKE '%,38,%'
OR Col1 LIKE '38,%'
)
OR
(
col2 = '38'
OR col2 LIKE '%,38'
OR col2 LIKE '%,38,%'
OR col2 LIKE '38,%'
)
OR
(
col3 = '38'
OR col3 LIKE '%,38'
OR col3 LIKE '%,38,%'
OR col3 LIKE '38,%'
)
Is there a way make it smarter/shorter/faster?
Thanks.!
You can use the function FIND_IN_SET(). MySQL has a dedicated function FIND_IN_SET() that returns field index if the value is found in a string containing comma-separated values.
Example
DROP TABLE table_name;
CREATE TABLE table_name
(col1 VARCHAR(100));
INSERT INTO table_name VALUES ('38');
INSERT INTO table_name VALUES ('37,38,39');
INSERT INTO table_name VALUES ('37,38');
INSERT INTO table_name VALUES ('38,39');
INSERT INTO table_name VALUES ('48');
SELECT col1
FROM table_name
WHERE FIND_IN_SET(38, col1) > 0;
Your solution would be
SELECT col1, col2, col3
FROM table_name
WHERE FIND_IN_SET(38, col1) > 0
OR FIND_IN_SET(38, col2) > 0
OR FIND_IN_SET(38, col3) > 0 ;
I have a table in MySQL as below:
ID, COL1, COL2 VALUE
'1', 'OBJ1', 'OBJ2', '5'
'2', 'OBJ1', 'OBJ2', '1'
'3', 'OBJ2', 'OBJ1', '3'
'4', 'OBJ3', 'OBJ1', '4'
'5', 'OBJ3', 'OBJ4', '6'
Relation between col1 and col2 is independent of position, ie OBJ1 in col1 and OBJ2 in col2 is same as OBJ1 in col2 and OBJ2 in col1. This means that OBJ1 and OBJ2 shares a relationship.
Now, this means that the object OBJ1 and OBJ2 have a value of 1,5,3...
I want to keep only distinct values ie OBJ1, OBJ2 should occur only once in the table, not even OBJ2,OBJ1.
Importantly, I want to retain only the row with HIGHEST value.
The result I want is thus:
ID, COL1, COL2 VALUE
'1', 'OBJ1', 'OBJ2', '5'
'4', 'OBJ3', 'OBJ1', '4'
'5', 'OBJ3', 'OBJ4', '6'
What is the best and efficient way of doing this? I have over 10 million rows.
I have searched in many forums/Google but cannot find the exact answer I am looking for..
Try this:
SELECT t1.ID, t1.COL1, t1.COL2, t1.VALUE
FROM mytable AS t1
JOIN (
SELECT LEAST(COL1, COL2) AS C1,
GREATEST(COL1, COL2) AS C2,
MAX(VALUE) AS max_Value
FROM mytable
GROUP BY LEAST(COL1, COL2),
GREATEST(COL1, COL2)
) AS t2 ON t1.COL1 = t1.C1 AND t1.COL2 = t2.C2 AND t1.VLAUE = t2.max_Value
You could use an in clause and subselect grouped by
for solve also the problem related to the distinct pair combination
You should organize the data in a proper way
select
id
, case when col1 <= col2 then col1 else col2 end COL1
, case when col1 > col2 then col1 else col2 end COL2
, value
from start_table
then the query became
SELECT t1.ID, t1.COL1, t1.COL2, t1.VALUE
FROM (
select
id
, case when col1 <= col2 then col1 else col2 end COL1
, case when col1 > col2 then col1 else col2 end COL2
, value
from start_table
) t1
where value in (
select max(value)
FROM (
select
id
, case when col1 <= col2 then col1 else col2 end COL1
, case when col1 > col2 then col1 else col2 end COL2
, value
from start_table
) mytable
group by col1, col2
)
or using an inner join
SELECT t1.ID, t1.COL1, t1.COL2, t1.VALUE
FROM (
select
id
, case when col1 <= col2 then col1 else col2 end COL1
, case when col1 > col2 then col1 else col2 end COL2
, value
from start_table
) t1
inner join
(
select max(value) as value
FROM (
select
id
, case when col1 <= col2 then col1 else col2 end COL1
, case when col1 > col2 then col1 else col2 end COL2
, value
from start_table
) mytable
group by col1, col2
) T2 on t1.value = t2.value
Rebuild the table so that no dups are allowed; in the process, get rid of the dups. (And get rid of the apparently useless id.)
CREATE TABLE new (
col1 ...,
col2 ...,
`value` ...,
PRIMARY KEY(col1, col2),
INDEX(col2, col2, `value`)
) ENGINE=InnoDB;
INSERT INTO new (col1, col2, `value`)
SELECT LEAST(col1, col2),
GREATEST(col1, col2),
`value`
ON DUPLICATE KEY UPDATE
`value` := GREATEST(`value`, VALUES(`value`));
RENAME TABLE real TO old,
new TO real;
DROP TABLE old;
In the future, you will need this for INSERTing/UPDATEing new rows:
INSERT INTO new (col1, col2, `value`)
VALUES (?, ?, ?)
ON DUPLICATE KEY UPDATE
`value` := GREATEST(`value`, VALUES(`value`));
(This assumes you want to increase value whenever it is already in the table.)
These save space and speed (important for 10M rows): Getting rid of id; having optimal indexes; using InnoDB; etc.
Here's my SELECT query:
SELECT col1, col3, col5, col8
FROM Table1
In my SELECT query, I want to perform a COUNT(*) exclusively for the current row.
I want something like this, but have no idea how I can get this:
SELECT col1, col3,
(
SELECT COUNT(*)
FROM table1 WHERE col3 = col3 value for current row
),
col5, col8
FROM Table1
What is the correct way to perform a COUNT(*) for the current row of a SELECT query resultset?
try this:
set #num := 0;
SELECT #num := #num+1 , col1, col3, col5, col8 FROM Table1
or other way:
SET #num := ( SELECT COUNT( * ) FROM Table1) ;
SELECT #num := #num -1 , col1, col3, col5, col8
FROM Table1
SELECT col1, col3,
(
SELECT COUNT(*)
FROM table1 WHERE id = A.Id
) Count,
col5, col8
FROM Table1 A
Found it.
If I write my query like this:
SELECT col1, col3,
COUNT(*) AS count,
col5, col8
FROM Table1
then I get COUNT of all the items in Table1 for all rows.
I actually wanted COUNT of all items for selective rows.
Like I may have col3 value appearing more than once. I actually want the count of all items for each col3.
So, GROUP BY clause is the solution.
SELECT col1, col3,
COUNT(*) AS Count,
col5, col8
FROM Table1
GROUP BY col3
Sorry, I think I wasn't able to explain my problem properly, so it confused a lot of people.. A very poor question. My bad.
Suppose, a select operation is giving 3 columns: col1, col2 and col3. col2 and col3 are of type time. I want the result to order by the time-stamp. For each record, time-stamp is equal to col3 if col3 is Not null, else it's col2. How to do this?
Use the built-in function ifnull():
select
...
order by ifnull(col3, col2)
ifnull() returns the first parameter if it is not null, otherwise the second parameter.
You can do it using subqueries. In the internal query you check if col3 is NULL and you "select" col3 or col2 AS "my_time". And then, in the external query, you order by "my_time".
Sub-query example:
SELECT <whatever>, IF (col3 IS NOT NULL, col3, col2) AS my_time FROM <table>
And then, the external query:
SELECT * FROM (
SELECT <whatever>, IF (col3 IS NOT NULL, col3, col2) AS my_time FROM <table>
) AS <temp_table> ORDER BY <temp_table>.my_time