I'm working on following query:
INSERT INTO a (id, value) VALUES (_id, (SELECT value FROM b WHERE b.id = _id));
Table a: id, value (has a default value)
Table b: id, value
Table b does not contain all requested values. So the SELECT query sometimes returns 0 rows. In this case it should use the default value of a.value.
Is this somehow possible?
Edit:
Solution for empty columns in comments of the post marked as solved.
you can wrap the value in coalesce(max(value), default_value)
INSERT INTO a (id, value)
VALUES (_id, (SELECT coalesce(max(value), default_value)) FROM b WHERE b.id = _id));
The following query would work. First the max(value) is looked up from table b for _id. It would be either NULL or equal to b.value. If it is NULL (checked using the COALESCE function), then the default value of the value column of table a is set as the value.
The default value of the value column of table a is accessed using the DEFAULT function (please refer Reference 1).
INSERT INTO a
SELECT
_id,
COALESCE(max(value), (SELECT DEFAULT(value) FROM a LIMIT 1)) value
FROM b
WHERE id = _id;
SQL Fiddle demo
Reference:
How to SELECT DEFAULT value of a field on SO
If MySQL follows other RDBMS behaviour, the default is only picked up when you don't even specify the field. This means that you need two different INSERT statements:
IF (EXISTS(SELECT * FROM b WHERE id = _id)) THEN
INSERT INTO a (id, value) SELECT _id, value FROM b WHERE id = _id;
ELSE
INSERT INTO a (id) SELECT _id;
END IF;
Or, possibly, something like this...
INSERT INTO a (id, value) SELECT _id, value FROM b WHERE id = _id;
IF ((SELECT ROW_COUNT()) = 0) THEN
INSERT INTO a (id) SELECT _id;
END IF;
Please note, this is conceptual. I've looked up the syntax for you, but I haven't tested it on MySQL.
Related
I want to ignore duplicates (or update key on duplicates), but only on consecutive duplicates.
Say my initial table looks like this (uk and a are column names):
uk a
----
x 1
Iteration 1 inserts 1 so I want this to be ignored in order to avoid duplicates.
Iteration 2 inserts 2 and my table now looks like this:
uk a
----
x 1
x 2
Iteration 3 inserts 1 and because the last row where my unique key = x was different to 1 then I want 1 to be inserted again:
uk a
----
x 1
x 2
x 1
How can this be achieved in MySQL?
My current solution is to query in data from the table first and remove these duplicates, but I would prefer that it was handled by MySQL.
You need a column that will be an auto-increment primary key
CREATE TABLE your_table(
id INT NOT NULL AUTO_INCREMENT,
uk CHAR(30) NOT NULL,
a INT,
PRIMARY KEY (id)
);
INSERT INTO your_table(uk, a) VALUES ('x', 1)
now you can use the following insert command to avoid duplicates as you describe it
INSERT INTO your_table(uk, a)
SELECT 'x', 1 FROM your_table t1
JOIN (
SELECT max(id) maxid, uk
FROM your_table
GROUP BY uk
) t ON t.maxid = t1.id and
t1.a != 1 and
t.uk = 'x'
The second insert can be the following
INSERT INTO your_table(uk, a)
SELECT 'x', 2 FROM your_table t1
JOIN (
SELECT max(id) maxid, uk
FROM your_table
GROUP BY uk
) t ON t.maxid = t1.id and
t1.a != 2 and
t.uk = 'x'
The third insert will be the same as the first one and the result table will be as expected.
See the demo
From your table it is not visible, which values got inserted last. Data in a table is considered unordered. So for your last example we know there are the three records x|1, x|1, x|2 in the table, but not whether x|1 or x|2 was inserted last. You'd need an additional column to indicate this. This could be a datetime or an ascending ID.
If you don't want to change your table, you need a helper table containing the last record instead. Anyway, you'd write a before-insert trigger to look up the last inserted value and throw an error when the new record matches the last inserted record for th uk.
create table mytable(uk char(1), a int);
create table mytable_helper(uk char(1), a int, primary key (uk));
create trigger mytable_ins BEFORE INSERT ON mytable FOR EACH ROW
begin
DECLARE msg VARCHAR(128);
if exists (select * from mytable_helper h where new.uk = h.uk and new.a = h.a) then
set msg = concat('Consecutive duplicate for a = ', new.a, ' and uk = ''', new.uk, '''.');
SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = msg;
else
replace into mytable_helper (uk, a) values (new.uk, new.a);
end if;
end;
insert into mytable (uk, a) values ('x', 1);
insert into mytable (uk, a) values ('x', 2);
insert into mytable (uk, a) values ('x', 1);
insert into mytable (uk, a) values ('y', 3);
insert into mytable (uk, a) values ('x', 1);
Error(s), warning(s):
Consecutive duplicate for a = 1 and uk = 'x'.
REXTESTER http://rextester.com/XOG65602
How do I insert a sql row into a new table where it meets criteria but resets the id value. In other words, copy the row, but reset the id value.
This is my current sql
INSERT INTO followers_lost SELECT * FROM followers WHERE pk = $pk
I tried to SET id=null and VALUE (0), but both don't work.
All you have to do since you want all the columns except the identity is specify all the non-identity columns on the insert:
INSERT INTO [followers_lost] ([Column1],[column2]...{but not the identity
column})
SELECT [Column1],[column2]...{but not the identity column} FROM followers WHERE
pk = $pk
You can create the column and then update it:
SET #new_id=0;
UPDATE your_table
SET id = #new_id := #new_id + 1
where id = 0
OK based on your comment I think you are trying to take all or some of the fields from Followers except the PK and put them into Followers_Lost where they equal a certain PK. If you want multiple PK's you would need to change the where clause to an IN statement instead of an equal and adjust your values accordingly.
CREATE TABLE dbo.UAT_Followers_Lost (PK INT IDENTITY(1,1),DATA VARCHAR(50) )
CREATE TABLE dbo.UAT_Followers (PK INT IDENTITY(1,1),DATA VARCHAR(50) )
INSERT INTO dbo.UAT_Followers
(DATA)
SELECT 'Jan'
UNION ALL
SELECT 'Feb'
UNION ALL
SELECT 'Mar'
DECLARE #PK INT
SET #PK = 1
INSERT INTO dbo.UAT_Followers_Lost
(Data)
SELECT Data
FROM dbo.UAT_Followers
WHERE PK = #PK
I have a table in mysql like this (the id is primary key):
id | name | age
1 | John | 46
2 | | 56
3 | Jane | 25
Now I want to update the name only if this is empty. If the value is not empty it should duplicate the row with a new id else it should update the name.
I thought it could be done with an if-statement but it doesn't work.
if((select `name` from `table1` where `id` = 3) = '',
update `table1` set `name`='ally' where `id` = 3,
insert into `table1` (`id`,`name`,`age`) values
(4, 'ally', select `age` from `table1` where `id` = 3))
EDIT:
With Spencers answer I made it working using an if in the code. (However I would still like a way to do just a single mysql query).
db.set_database('database1')
cursor = db.cursor()
query = "select IF(CHAR_LENGTH(name)>0,1,0) from table1 where id = {0}".format(id)
cursor.execute(query)
val1 = cursor.fetchone()
if val1[0]:
query = "INSERT INTO `table1` (`id`,`name`,`age`) SELECT {0},{1},`age` FROM `table1` WHERE `id` = {2}".format(new_id, name, id)
cursor.execute(query)
else:
query = "update `table1` set `name` = '{0}' where `id` = {1}".format(name, id)
cursor.execute(query)
db.commit()
If you make like this :
select t.*,
if(
EXISTS(select n.name from table1 n where n.id = 2 and NULLIF(n.name, '') is null) ,
'true',
'false'
) from table1 t
if statement returns "true", becouse in your table exist row where id =2 and name is empty.
like this example, You can edit your query :
if(
EXISTS(select n.name from table1 n where n.id = 3 and NULLIF(n.name, '') is null),
update `table1` set `name`='ally' where `id` = 3,
insert into `table1` (`id`,`name`,`age`) values
(4, 'ally', select `age` from `table1` where `id` = 3)
)
IF is not a valid MySQL statement (outside the context of a MySQL stored program).
To perform this operation, you'll need two statements.
Assuming that a zero length string and a NULL value are both conditions you'd consider as "empty"...
To conditionally attempt an update of the name field, you could do something like this:
UPDATE table1 t
SET t.name = IF(CHAR_LENGTH(t.name)>0,t.name,'ally')
WHERE t.id = 3 ;
The IF expression tests whether the current value of the column is "not empty". If it's not empty, the expression returns the current value of the column, resulting in "no update" to the value. If the column is empty, then the expression returns 'ally'.
And you'd need a separate statement to attempt an INSERT:
EDIT
This isn't right, not after a successful UPDATE... of the existing row. The attempt to INSERT might need to run first,
INSERT INTO table1 (id,name,age)
SELECT 4 AS id, 'ally' AS name, t.age
FROM table1 t
WHERE t.id = 3
AND CHAR_LENGTH(t.name)>0;
We need a conditional test in the WHERE clause that prevents a row from being returned if we don't need to insert a row. We don't need to insert a row if the value 'ally' ...
The use of CHAR_LENGTH >0 is a convenient test for string that is not null and is not zero length. You could use different test, for however you define "empty". Is a single space in the column also considered "empty"?)
Okay here is the situation:
I the following data in a table.
PAIR_NO NO NO2
3 5678EFGH 1234ABCD
4 1111BBBB 0000AAAA
1 1234ABCD 5678EFGH
2 0000AAAA 1111BBBB
The constraints are if no = no2 in another row skip that row.
So in this sample data the only rows that would be selected should be pair no 3 and 4.
I have tried to merge and inner join with self but I just keep getting all 4 rows back.
I have tried to insert into a table where not exists but again I get 4 rows inserted.
SELECT a.* from PAIRS a
inner join PAIRS b on a.no=b.no2 and a.no2=b.no;
I was thinking maybe selecting distinct number from column 1 and then check those in column 2 but I think that would yield the same four rows.
I may be over thinking this problem and maybe some here can look at this and see where the solution is hiding.
I am currently testing this on MySQL but it should run on SQLServer 2008. I have searched but all the questions didn't seem to match my data set issue.
Taking you at your word, meaning selecting all records where the value of no column does not appear anywhere in no2 column in the same table, try this:
SELECT A.PAIR_NO, A.NO, A.NO2
FROM PAIRS A
LEFT JOIN PAIRS B ON(A.NO = B.NO2)
WHERE B.PAIR_NO IS NULL -- assuming this column is not nullable
Another option is to use NOT EXISTS:
SELECT PAIR_NO, NO, NO2
FROM PAIRS A
WHERE NOT EXISTS(
SELECT 1
FROM PAIRS B
WHERE B.NO2 = A.NO
)
I personally prefer the LEFT JOIN option since it's shorter and more readable.
Both of these statement should work on both MySql and Sql Server.
Okay fellas I want to thank you all for helping, but I think I solved my issue. Took me a second but I believe this is what I am after (SQL Server 2008):
if OBJECT_ID('tempdb..#pairs') is not null drop table #pairs
if OBJECT_ID('tempdb..#pairs_final') is not null drop table #pairs_final
create table #pairs(pair_no int, a_no varchar(17),a_no2 varchar(17))
create table #pairs_final(pair_no int Identity(1,1), a_no varchar(17),a_no2 varchar(17))
insert into #PAIRS values(1,'1234ABCD','5678EFGH');
insert into #PAIRS values(1,'1234ABCD','XXXX9999');
insert into #PAIRS values(2,'0000AAAA','1111BBBB');
insert into #PAIRS values(3,'5678EFGH','1234ABCD');
insert into #PAIRS values(4,'1111BBBB','0000AAAA');
insert into #PAIRS values(1,'XXXX9999','1234ABCD');
insert into #pairs_final
select a.a_no,a.a_no2 from #pairs a
join (
select distinct a_no_p from(
select pair_no,a_no_p,
ROW_NUMBER() over (partition by pair_no order by a_no_p) as RN
from #pairs
unpivot(
a_no_p for clms in (a_no2,a_no)
) as umpvt
) as mypairs
where RN = 1
) as my_pairs on my_pairs.a_no_p=a.a_no
select * from #pairs_final
This will give me the following results:
pair_no a_no a_no2
1 1234ABCD 5678EFGH
2 1234ABCD XXXX9999
3 0000AAAA 1111BBBB
Hope this might help someone else.
Enjoy.
DECLARE #TBL AS TABLE
(
[NO] INT,
[CODE] VARCHAR(50),
[AREA] VARCHAR(50)
)
/* EXAMPLE 1 */
INSERT INTO #TBL([NO],[CODE],[AREA]) VALUES (1,'001','A00')
INSERT INTO #TBL([NO],[CODE],[AREA]) VALUES (2,'001','A00')
INSERT INTO #TBL([NO],[CODE],[AREA]) VALUES (3,'001','B00')
INSERT INTO #TBL([NO],[CODE],[AREA]) VALUES (4,'001','C00')
INSERT INTO #TBL([NO],[CODE],[AREA]) VALUES (5,'001','C00')
INSERT INTO #TBL([NO],[CODE],[AREA]) VALUES (6,'001','A00')
INSERT INTO #TBL([NO],[CODE],[AREA]) VALUES (7,'001','A00')
/* EXAMPLE 2 */
/* ***** USE THIS CODE TO ENTER DATA FROM DIRECT TABLE *****
SELECT
ROW_NUMBER() OVER(ORDER BY [FIELD_DATE]) AS [NO]
,[FIELD_CODE] AS [CODE]
,[FIELD_AREA] AS [AREA]
FROM TABLE_A
WHERE CAST([FIELD_DATE] AS DATE) >= CAST('20200307' AS DATE)
ORDER BY [FIELD_DATE],[FIELD_CODE]
*/
SELECT
A.NO AS ANO
,A.CODE AS ACODE
,A.AREA AS AAREA
,B.NO AS BNO
,B.CODE AS BCODE
,B.AREA AS BAREA
,CASE WHEN A.AREA=B.AREA THEN 'EQUAL' ELSE 'NOT EQUAL' END AS [COMPARE AREA]
FROM #TBL A
LEFT JOIN #TBL B
ON A.NO=B.NO+1
A nearly identical question was asked here using an IF statement, but he didn't get an actionable answer, just suggested to go here where no IF statements are being used. I've tried to write both an IF statement and a conditional statement using the latter link but I'm stuck (see below).
I want to be able to conditionally insert a row only if the previous insert attempt actually inserted a row (ROW_COUNT > 0). The previous insert could have been duplicate data, so I'm deliberately setting it's LAST_INSERT_ID to null so no subsequent child inserts can occur with that LAST_INSERT_ID. The SQL script is created by a C# script, so it would be very possible that the LAST_INSERT_ID is not pointing to where you'd expect.
Here's a very small example of the script generated code (there are ~3 million rows in the final database):
SET #Vendors_Vendor_ID = (SELECT vendor_ID FROM VENDORS WHERE vendorName = 'PCA');
INSERT IGNORE INTO PCBID (PCBID, PCBDrawing, AssemblyDrawing, PONumber, Vendors_Vendor_ID)
VALUES (11001, '10405', '41606', '091557.5', #Vendors_Vendor_ID);
SET #eventType_ID = (SELECT EVENTTYPE_ID FROM EVENTTYPES WHERE EVENTTYPE = 'Creation');
SET #USER = 'CTHOMAS';
INSERT IGNORE INTO EVENTS (PCBID, EVENTTYPE_ID, DATETIME, USER)
VALUES (11001, #eventType_ID, '2009-06-15T13:15:27', #USER);
SET #EVENT_ID = IF(ROW_COUNT() > 0, LAST_INSERT_ID(), null);
-- THIS DOES NOT WORK
SELECT IF(#EVENT_ID != null,
INSERT INTO EVENTDETAILS (EVENT_ID, ITEMNAME, ITEMVALUE)
VALUES (#EVENT_ID, 'Notes', 'WO#89574'),
null);
-- THIS DOESN'T WORK EITHER
INSERT INTO EVENTDETAILS (EVENT_ID, ITEMNAME, ITEMVALUE)
SELECT #EVENT_ID, 'Notes', 'WO#89574'
WHERE #EVENT_ID != null;
The PCBID table is not a problem for duplicate data, and the Events table has a composite unique key which prevents duplicate data by using INSERT IGNORE:
CREATE TABLE IF NOT EXISTS `uniqueTest`.`events` (
`Event_ID` INT(11) NOT NULL AUTO_INCREMENT ,
`PCBID` INT(11) NOT NULL ,
`EventType_ID` INT(11) NOT NULL ,
`DateTime` DATETIME NOT NULL ,
`User` VARCHAR(45) NOT NULL ,
PRIMARY KEY (`Event_ID`) ,
UNIQUE KEY `PDU_Index` (`PCBID`, `DateTime`, `User`),
The Problem:
I need to be able to do a conditional insert based on the previous insert attempt into the Events table, if it was ignored (because it's duplicate data), don't insert any child rows either. There's currently no way to make any of the EventDetail data unique, there could be multiple rows of legitimate data based on a given Event_ID.
There are four levels deeper possible below the Events table depending on what type of data it is, if the event data doesn't get inserted because it's duplicate data, no child data gets written either (because it'll be duplicate as well).
Your second try was nearly right. You've got to check of NULL values with IS NOT NULL. So use
INSERT INTO EVENTDETAILS (EVENT_ID, ITEMNAME, ITEMVALUE)
SELECT #EVENT_ID, 'Notes', 'WO#89574' FROM DUAL
WHERE #EVENT_ID IS NOT NULL; -- instead of !=
or
INSERT INTO EVENTDETAILS (EVENT_ID, ITEMNAME, ITEMVALUE)
SELECT t.* FROM (
SELECT #EVENT_ID, 'Notes', 'WO#89574'
) t
WHERE #EVENT_ID IS NOT NULL; -- instead of !=
The first one cannot work:
-- THIS DOES NOT WORK
SELECT IF(#EVENT_ID != null,
INSERT INTO EVENTDETAILS (EVENT_ID, ITEMNAME, ITEMVALUE) ...
because the syntax of IF is
IF(expr1,expr2,expr3)
If expr1 is TRUE (expr1 <> 0 and expr1 <> NULL) then IF() returns expr2; otherwise it returns expr3. IF() returns a numeric or string value, depending on the context in which it is used.
Conditional execution of statements is only possible in stored routines. The IF syntax of stored routines would allow something like
IF #EVENT_ID IS NOT NULL THEN
INSERT INTO EVENTDETAILS (EVENT_ID, ITEMNAME, ITEMVALUE) ...
END IF
You've got to distinguish those both syntax versions.