Normalization of Many to Many relation in sql -

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i have product table contains 2 column

productid   desc   1         fan   2         table   3         bulb

i have table contains supplier information

supplierid    desc    1          abc    2          xyz    3          hjk

now 1 supplier can supply multiple products , 1 product can supplied multiple suppliers achieve have created table tbl_supplier_product

 supplierid    productid       1            1      1            2      2            1      2            2      2            3

is way link table supplier , product table through primary composite key. in table primary key composite key (supplierid , productid) or should add column row id each record , use primary key , add unique constraint columns supplierid , productid

 supplierid    productid    row id          1            1       1          1            2       2          2            1       3          2            2       4          2            3       5 unique constraint(supplierid, productid)

what relationship of table supplier table? bit confused here because added table resolve many many relationship , redundant data still seems table has many many relationship both tables??

you don't need column: composite key need

i create unique index reverse of pk too: useful many queries , provides fk index productid

after comment: 

create table supplierproduct (     supplierid int not null,     productid int not null,      primary key (supplierid, productid) ); go create unique nonclustered index ixu_reversepk on supplierproduct (productid, supplierid); go

for more

and use ensure fks have indexes

select  fk.name [missing fk index]    sys.foreign_keys fk   exists         (         select  *            sys.foreign_key_columns fkc           fkc.constraint_object_id = fk.object_id                 , not exists                 (                 select  *                    sys.index_columns ic                   ic.object_id = fkc.parent_object_id                         , ic.column_id = fkc.parent_column_id                         , ic.index_column_id = fkc.constraint_column_id                 )         ); go

in erd (random 1 powerpoint have):

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