Contents
When to return all rows from a table?
When no match is found any columns in the SELECT column list that are from the table which is not going to return all rows will contain . We can see this in the last row of the resultset returned by the query where the row for Bill Gates has no related data in the TrainingTaken table.
How to return rows from left table not found in right table?
FROM first_table f LEFT JOIN second_table s ON f.key=s.key WHERE s.key is NULL I also like to use NOT EXISTS. When it comes to performance if index correctly it should perform the same as a LEFT JOIN or better. Plus its easier to read.
How to select all rows from one table?
A: Conceptually, we select all rows from table1 and for each row we attempt to find a row in table2 with the same value for the name column. If there is no such row, we just leave the table2 portion of our result empty for that row. Then we constrain our selection by picking only those rows in the result where the matching row does not exist.
How do you return rows from outer join in SQL?
If we use the RIGHT keyword then all rows from the table on the right hand side of the JOIN keyword are returned. In the above example the JOIN is defined as a LEFT outer join and the table that falls on the LEFT side of the JOIN keyword is the Employee table so all rows from the employee table will be returned.
How to check if two tables have identical content?
The count of this subquery will be equal to the count of EmpDtl1 if and only if EmpDtl2 does not contribute any rows to the result i.e. the two tables are identical. Alternatively, dump the tables in key sequence to two text files and use your comparison tool of choice.
How to combine two tables into a single table?
Now I wish to have a single table that will include all the rows of both tables, with a single ID column and a single Category_name column (total of 14 columns). So in case the same ID has 3 records in table 1 and another 5 records in table 2 I wish to have all 8 records (8 rows)
How to select all records from one table that does not exist?
This is the strategy: you create two implicit temporary tables and make a union of them. The first temporary table comes from a selection of all the rows of the first original table the fields of which you wanna control that are NOT present in the second original table.