`3` querys for the same thing?

[Xhavick Past]

Hi everyone, I'm relatively new in sql language, so i have one question i hope somebody can help me.

I'm trying to insert new rows in a table that have index with no primary keys and without unique, then i want to prevent from insert duplicate a DATE that already exists in the primary table.

First thing first:

fec_informacion date
sdo_real_e int
nombre varchar(50)

then

INSERT INTO tb1 (FEC_INFORMACION, SDO_REAL_E, NOMBRE)
SELECT FEC_INFORMACION, SDO_REAL_E, NOMBRE
FROM tb2

# NOW TO PREVENT DUPLICATE ROWS I've tried with 3 different options. It appears to be the same result. I need to confirm that, because i really don't find any difference in my tests. The 3 options los like:

# WHERE fec_informacion NOT IN(SELECT fec_informacion FROM tb1);

# WHERE tb2.FEC_INFORMACION > (select max(fec_informacion) from tb1);

# WHERE NOT EXISTS(SELECT FEC_INFORMACION FROM tb1 where tb1.FEC_INFORMACION = tb2.FEC_INFORMACION);

Anticipated thanks to all for read this.