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Why do attributes have null or empty values after a join?
After performing a join between a feature class and a stand-alone table, such as dBASE IV, dBASE V, CSV, or PRN, the values in the fields from the joined table are empty or null. Null values can be the result of several factors:
Why is left join returning ” null ” Records when with where?
In the 2nd case the rows get filtered out based on the values of the rank column after the OUTER JOIN (LEFT JOIN here) is performed. Hence, the rows with NULL values in the rank column are filtered out.
Is the where and left join condition the same?
A left join condition and where condition filter are not both same. Data is filtered by the where clause after the physical join is done. if you look a left join it will normally return every row from your left table, but once you have a where clause, it will filter the output of the join so the result is like an inner join.
Why is The isnull function in the join clause?
Although the ISNULL function is handy, if you are doing large joins having this function in the join clause will slow down the query. A lot of this will also depend on the indexes you have setup and how the indexes are used for the join.
What happens when you join fields between CSV and shp?
When you join the fields between your .csv and your .shp (for example), be sure that the Type are the same (see in Properties of both file). For example: my FID for my shp was in real as my ID for my csv was in integer. After the join, I get “NULL”.
Why are all the fields in the shapefile null?
When I compare the values of the GISJOIN fields in each table to each other, they match up perfectly. HOWEVER when I perform the join, inside the Properties dialog, and then look at the shapefile’s attribute table, all the new attribute headings are there, added in, but all the values are “NULL.”
What should be included in the join field?
Before considering any table joins, the most vital aspect to consider is the JOIN FIELD. The join field must contain matching values (in the same format, such as STRING or INTEGER) in both the source table and the target layer.