使用 2 where 条件将记录插入 postgres 数据库

Question

I'm trying to insert data into a table based on whether a record exists with the same ID and DATE. I've put the code in a loop that does the insertion query for every record in the students_present variable. HERE'S THE CODE

for ID in students_present:
    STUDENTID = 'SELECT STUDENTID FROM encodings WHERE STUDENTID = ID'
    STUDENTNAME = 'SELECT STUDENTNAME FROM encodings WHERE STUDENTID = ID'
    STUDENTEMAIL = 'SELECT STUDENTEMAIL FROM encodings WHERE STUDENTID = ID'
    insert_script = "INSERT INTO meeting1(STUDENTID, STUDENTNAME, STUDENTEMAIL, MEETINGDATE, MEETINGTIME) WHERE ID IN STUDENTID AND MEETINGDATE <> GETDATE() VALUES ('{}','{}','{}','GETDATE()','CURRENT_TIMESTAMP')".format(STUDENTID, STUDENTNAME, STUDENTEMAIL)
    cur.execute(insert_script)

I believe my error arrises from how I've written the condition as it reflects this error:

syntax error at or near "WHERE"
LINE 1: INSERT INTO meeting1 WHERE ID IN STUDENTID AND MEETINGDATE <...

Any advice on how to go about this?

Answer 1

I created a Unique constraint key for the particular columns that I wanted to be unique by running

ALTER TABLE table_name
ADD CONSTRAINT constraint_name UNIQUE (column1, column2);

This will create a key that is a combination of column1 and column2 for which a record cannot exist with the same values in both columns.

for example if column1 is named Month and column2 named Year, I can only have one record like May 2022 for the Month and Year columns respectively. Once I enter another record with both month and year as May 2022 I'll get a duplicate key error on that constraint.

I hope this helps someone.