I have a sql table that has two columns id and name. I have list of names about 20 and I need to write a query that checks if name exists before insert.
Is there a better way of doing this rather then just having the below query 20 times but with different names (I need do this in t-sql):
IF NOT EXISTS(SELECT*
FROM mytable
WHERE name = 'Dan')
BEGIN
INSERT INTO mytable
(name)
VALUES ('dan')
END
INSERT INTO MyTable (Name)
SELECT NewNames.Name
FROM ( VALUES ('Name1'), ('Name2'), ('Name3') ) AS NewNames (Name)
WHERE NOT EXISTS ( SELECT 1
FROM MyTable AS MT
WHERE MT.Name = NewNames.Name );
from clause? Can it be in the millions?I think you could use a merge statement:
MERGE INTO myTable AS Target
USING (VALUES ('name1'),('name2'),('...')) AS source (NAME)
ON Target.NAME = Source.NAME
WHEN NOT MATCHED BY TARGET THEN
INSERT (NAME) VALUES (name)
You can filter values with NOT EXISTS
INSERT INTO myTable (
Name
)
SELECT DISTINCT
Name
FROM (
VALUES ('Name 1'),
('Name 2')
) AS NewNames(Name)
WHERE
NOT EXISTS (SELECT 1 FROM TargetTable WHERE myTable.Name = NewNames.Name)
If your new names are in another table, you can change the select query in the above one.
Please note, that the DISTINCT keyword is necessary to filter out the duplications in the source data.
I would do this using insert:
with names as (
select 'Dan' as name union all
select 'name2' union all
. . .
)
insert into myTable(name)
select distinct name
from myTable
where not exists (select 1 from mytable t2 where t2.name = t.name);
Note: you may want to create a unique index on mytable(name) so the database does the checking for duplicates.
INSERT INTO MyTable (Name)
SELECT Name FROM
(
VALUES ('Name 1'),
('Name 2')
) AS Names(Name)
WHERE Name NOT IN
(
SELECT Name FROM MyTable
)
untested so there might be some minor errors:
merge into mytable x
using (
values ('name1')
, ('name2')
, ...
, ('namen')
) as y (name)
on x.name = y.name
when not matched then
insert (name)
values (y.name)
INSERT IGNORE INTO myTable (column1, column2) VALUES (val1, val2),(val3,val4),(val5,val6);
INSERT IGNORE will allow skip on duplicate values
Use INSERT INTO ... SELECT to insert data conditionally
Each row check with WHERE NOT EXISTS to prevent duplicates based on the column name
Use UNION ALL to combine all rows into a single query
INSERT INTO mytable (name)
SELECT * FROM (
SELECT 'Dan' AS name,
WHERE NOT EXISTS (SELECT 1 FROM mytable WHERE name = 'Dan')
UNION ALL
SELECT 'Bob'
WHERE NOT EXISTS (SELECT 1 FROM mytable WHERE name = 'Bob')
UNION ALL
SELECT 'Mike'
WHERE NOT EXISTS (SELECT 1 FROM mytable WHERE name = 'Mike')
) AS new_values;
INSERT INTO mytable ... WHERE Name NOT IN ('<Name1>', '<Name2>', '<Name3>'...)