Consider a table with 3 records which you already imported to hdfs using sqoop
+------+------------+----------+------+------------+
| sid | city | state | rank | rDate |
+------+------------+----------+------+------------+
| 101 | Chicago | Illinois | 1 | 2014-01-25 |
| 101 | Schaumburg | Illinois | 3 | 2014-01-25 |
| 101 | Columbus | Ohio | 7 | 2014-01-25 |
+------+------------+----------+------+------------+
sqoop import --connect jdbc:mysql://localhost:3306/ydb --table yloc --username root -P
Now you have additional records in the table but no updates on existing records
+------+------------+----------+------+------------+
| sid | city | state | rank | rDate |
+------+------------+----------+------+------------+
| 101 | Chicago | Illinois | 1 | 2014-01-25 |
| 101 | Schaumburg | Illinois | 3 | 2014-01-25 |
| 101 | Columbus | Ohio | 7 | 2014-01-25 |
| 103 | Charlotte | NC | 9 | 2013-04-22 |
| 103 | Greenville | SC | 9 | 2013-05-12 |
| 103 | Atlanta | GA | 11 | 2013-08-21 |
+------+------------+----------+------+------------+
Here you should use an bwith --check-column which specifies the column to be examined when determining which rows to import.
sqoop import --connect jdbc:mysql://localhost:3306/ydb --table yloc --username root -P --check-column rank --incremental append --last-value 7
The above code will insert all the new rows based on the last value.
Now we can think of second case where there are updates in rows
+------+------------+----------+------+------------+
| sid | city | state | rank | rDate |
+------+------------+----------+------+------------+
| 101 | Chicago | Illinois | 1 | 2015-01-01 |
| 101 | Schaumburg | Illinois | 3 | 2014-01-25 |
| 101 | Columbus | Ohio | 7 | 2014-01-25 |
| 103 | Charlotte | NC | 9 | 2013-04-22 |
| 103 | Greenville | SC | 9 | 2013-05-12 |
| 103 | Atlanta | GA | 11 | 2013-08-21 |
| 104 | Dallas | Texas | 4 | 2015-02-02 |
| 105 | Phoenix | Arzona | 17 | 2015-02-24 |
+------+------------+----------+------+------------+
Here we use incremental last modified where we will fetch all the updated rows based on date.
sqoop import --connect jdbc:mysql://localhost:3306/ydb --table yloc --username root -P --check-column rDate --incremental lastmodified --last-value 2014-01-25 --target-dir yloc/loc
