How to avoid repeated data insertion in SQL

Method 1: Set as the primary key

Method 2: Set uniqueness constraints

The code is as follows:	Copy code
Alter table your table name add constraint cons_01 unique (duplicate column name 1, duplicate column name 2, duplicate column name 3, duplicate column name 4, duplicate column name 5)

Method 3: Add an SQL statement to Judge

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If not exists (select 1 from tb where duplicate column name 1 = 'XX' and duplicate column name 2 = 'XX' and duplicate column name 3 = 'XX' and duplicate column name 4 = 'XX') Begin Insert... End

Avoid inserting the same data to ensure the uniqueness of the data. For example, the university student ID must be unique and cannot be repeated.