如何根据 Postgresql 中的列值是否相同而插入表中

Question

I am inserting data into a table looks like this

|   num   | name     |  value |
----------------------------------
|    1    | name1    |   1    |
|    2    | name2    |   1    |
|    3    | name3    |   1    |
|    4    | name4    |   2    |
|    5    | name5    |   3    |

I wanted to insert with where clause like insert into table (num, name, value) values(6,name,1) when (num and value together) not exist in any row together

I tried to select first and insert on basis of that result but I think that is not the best way I want it in a single query

tried like: select * from the table where name=$name and value= $value if I got result then not insert otherwise insert. It was done with two queries but i don't want it.

Any help will be appriciated.

Answer 1

Use a unique constraint to enforce uniqueness for (num, value) :

alter table t add constraint unq_t_num_value unique (num, value);

Then the database ensures that the integrity of the table -- that these values are unique. You don't have to do it explicitly.

Note that if the unique constraint is violated, you get an error and the insert is aborted (along with other rows that might be inserted). If you want to ignore the error instead, you can use on conflict ignore .

Answer 2

Basically, first you need to do check if record with same num and Value is already present in table or not. if it is present then don't insert else insert the new record.

for this you can try to insert value with procedure:

the below procedure will help based on your need:

create procedure InsertRecVali(@num int,@name varchar(max),@value int)

as 

begin

if not exist(select 1 from table where num=@num and value=@value)

insert into table values(@num,@name,@value)

Else 

PRINT 'Cannot Insert Duplicate Value'

End;

After creating procedure, execute this procedure by passing the the values which you want to insert in table.

so before inserting record in table, it will check if there is already record present in table with same num and value then it will not insert it and give error ' Cannot Insert duplicate Value '.

otherwise if the record with same num and value is not already present in table then only it will insert record in table.

below is the example to execute this procedure:

EXEC dbo.InsertRecVali(1,'abc',6)