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1. In the Contents pane on the left, right-click the DowntownParcels layer name and select Attribute Table.
2. Browse through all fields in the attribute table.

The HCAD_NUM field contains the unique 13-digit HCAD account number for each parcel. You are also provided with the owner name and address for each parcel, but not very much no other information. Fortunately, a tremendous amount of other information about the parcels can be obtained from HCAD in stand-alone standalone tabular format. In this case, you would like to know the particular land use for each parcel, such as residential, commercial, or industrial. This information is contained in a separate Land table, which you will now explorewas obtained from the HCAD Public Data Download website at the http://pdata.hcad.org/download/index.html.

1. Close the DowntownParcels attribute table.
2. In the Catalog pane, within the TabularData geodatabase Tabular geodatabase, right-click the Land table and selectAdd To Current MapMap.

Notice that the Land table has been added to the bottom of the Contents pane under a new Standalone Tables section. This is because the data table does not currently have a spatial data associated with it, so it cannot yet be displayed on the map and, therefore, cannot be listed by drawing order.

1. In the Contents pane, right-click the Land table and select Open.Scroll down and browse through all of the fields Open.

Notice that you are again provided with the unique 13-digit HCAD account number, but, this time, the field is labeled name is ACCOUNT, rather than HCAD_NUM, as it was in the DowntownParcels feature class attribute table. When you perform a join, you are able to specify the field names of the two common join fields, so it is okay for them to have different field names, so long as the actual data contained within the two fields is identical.

You are also provided with the land use code and the land use description for each parcel. In order to symbolize the parcels by land use, you will first need to join the land use table to the parcels feature class. You will now explore the various land use codes.

1. Right-click the LAND_USE_C field and select Sort Ascending.
2. Scroll down and browse through all of the land use codes and descriptions.

Notice how many different land use categories there are. For example, commercial land use is divided into very specific categories, such as Restaurant, Ice House, Bar/Lounge, Department StoreDay Care Center, Medical Office, and Bank. While it is great to have this information available, symbolizing so many different categories on a single map can make the map difficult to interpret. Instead, you would prefer it might be preferable to symbolize the parcels using more generalized land use categories. Fortunately, the City of Houston has created a lookup table that assigns each appraisal district land use code to one of ten generalized land use categories. You will now explore this lookup table.

1. In the Catalog pane, within the TabularData geodatabase Tabular geodatabase, right-click the LandUseCode_LookupTable table and select Add To Current Map.
2. In the Contents pane, right-click the LandUseCode_LookupTable table and select Open.
3. Scroll down and browse through browse through the land use descriptions and the associated group descriptions.

Notice that the COUNTY field tells you which county uses the particular land use code listed. “HCAD” stands for Harris County. If you scroll down to the bottom of the table, you will notice “FBCAD” and “MCAD” for Fort Bend County and Montgomery County, respectively. The LANDUSE_CODE and LANDUSE_DESCRIPTION fields should look familiar, since they contain the same information as the Land table you looked at previously. The GROUP_CODE and GROUP_DSCR fields store one of ten general land use categories that correspond to each specific land use code. In order to symbolize the parcels using these generalized land use categories, you will also need to join the lookup table to the land use table and the parcels feature class. You will perform the join using the land use code field that is common to both your land use table and your lookup table.

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1. For ‘Input Join Field’, use the drop-down menu to select the HCAD_NUM field.
2. For ‘Join Table’, use the drop-down menu to select the Land table.
3. For ‘Output Join Field’, use the drop-down menu to select the ACCOUNT field.
4. Ensure that the ‘Add Join' tool settings match those shown below and click Run.
   
   
   
   
5. RightIn the Contents pane, right-click the DowntownParcels layer and select Attribute Table.
6. Scroll to the right and browse through all fields.

Notice the four new fields added to the end of the DowntownParcels attribute table showing the land use for every parcel. This is an example of a successful tabular join.

Because you want to symbolize the parcels using the more generalized land use categories, you will now also join the LandUseCode_LookupTable table using the land use code as the common field.

1. In the Contents pane, right-click the DowntownParcels layer and select Joins and Relates > Add Join.
2. For ‘Input Join Field’, use the drop-down menu to select the Land.LAND_USE_C fieldto select the Land.LAND_USE_C field. If that field does not appear in the list, you may have skipped the step above and are still viewing the previous run of the Add Join tool, which has not been refreshed to load the newly joined fields.

Notice that when a previous join is still in place, the field names are appended with the name of the layer or table from which they are derived.

1. For ‘Join Table’, use the drop-down menu to select the LandUseCode_LookupTable table.
2. For ‘Output Join Field’, use the drop-down menu to select the LANDUSE_CODE field.
3. Click Run.
4. If Once the join is complete, if necessary, scroll to the far right in the DowntownParcels attribute table.

Notice that all of the values in the six newly joined fields are null. This is an indication that something is wrong with the join. The two most common reasons for a join not to work are either the data values in the two fields in the two separate fields used for the common join fields are not identical between tables or the standalone join table itself is not formatted correctly for import into ArcGIS, which should would only occur if the outside table it is brought in from another file format, such as Excel or a CSV. In this case, the stand-alone standalone join table was already in a native ArcGIS file geodatabase, so there should not be a problem with the overall table formatting. Instead, you will look into the actual values stored in the land use code field in both tables for any discrepancies.

Troubleshooting Joins

You will now examine the two tables more closely to determine why the desired join field did not show up in the’ Join Data’ paneresulted in null values.

1. In the Contents pane, right-click the Land table and select Open.
2. Right-click the LandUseCode_LookupTable table and select Open.

Notice at the top left of the ‘Table’ window, you see one tab for each of the two tables that are open, but you want to be able to examine both tables simultaneously.

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