Join vs EXISTS

I need to check for the existence of some row in a table, I tend to write always a condition like:

	`SELECT a, b, c`
	  `FROM a_table`
	 `WHERE EXISTS`
		   `(SELECT *  -- This is what I normally write`
			  `FROM another_table`
			 `WHERE another_table.b = a_table.b`
		   `)`

	Some other people write it like:

	`SELECT a, b, c`
	  `FROM a_table`
	 `WHERE EXISTS`
		   `(SELECT 1   --- This nice '1' is what I have seen other people use`
			  `FROM another_table`
			 `WHERE another_table.b = a_table.b`
		   `)`

When the condition is NOT EXISTS instead of EXISTS: In some occasions, I might write it with a LEFT JOIN and an extra condition (sometimes called an antijoin):

	`SELECT a, b, c`
	  `FROM a_table`
		   `LEFT JOIN another_table ON another_table.b = a_table.b`
	 `WHERE another_table.primary_key IS NULL`

======================================================================================================

	`SELECT column1, column2`
	`FROM table1`
	`WHERE EXISTS (`
	  `SELECT 1`
	  `FROM table2`
	  `WHERE table1.column3 = table2.column3`
	`)`


	`SELECT table1.column1, table1.column2`
	`FROM table1`
	`JOIN table2`
	`ON table1.column3 = table2.column3`