Merge Table pattern is used to merge the table variables from two parser output tables by paired keys, enabling the combination of config-lets from different paragraphs as well.

The Merge Table process follows three table merging rules: Full Join, Inner Join and Left Join.

• Full Join: Keep all the rows in each table no matter the paired keys are matched or not.
  
  
• Inner Join: only keep the rows with paired keys matched.
  
  
• Left Join: Take the left source table as criteria, and only keep the rows having left source table data.
  

Example of Merge Table

To define a Merge Table pattern, complete the following:

Prerequisites: Create several patterns in advance to get the corresponding parser output tables which will be used to define Merge Table pattern. 

• For Source Table 1: Create a paragraph pattern to parse variables $route_map_name, $control_list and $route_map_config.
  
  
• For Source Table 2: Create a collector pattern to parse the variables $prefix_name, $prefix_config.
  
  

Steps for defining Merge Table pattern:

1. Click +New Pattern > Advanced > Merge Table, then, a merge table pattern is created. 
   
   
2. In the Source Table field of the right pane of this merge table pattern, select two source tables (in this example, output tables route_map_config, Prefix from the current parser are selected) to be merged. 
   
   
3. Click + Paired Key, then select table columns as as the key for merging tables: Multiple paired keys can be added to define the column pairs to be merged. In this example, After adding a paired key, you can preview the outputs in the output area below.
   
4. Click Settings, then configure more advanced settings from the Settings window:
   
   
   1. Select columns in merge table: In this block, select the columns from the two tables to merge. All columns are selected by default. You can remove the unnecessary columns by unchecking the corresponding checkbox. 
   2. Table Merging Rule: Three table merging rules are supported: Full Join, Inner Join and Left Join. In this example, Left Join is selected.
      Full Join: Keep all the rows in each table no matter the paired keys are matched or not.
      Inner Join: only keep the rows with paired keys matched.
      Left Join: Take the left source table as criteria, and only keep the rows having left source table data.
      

      Note: Right Join and Outer Join methods are not supported in Merge Table pattern.

   3. Click OK to complete the merge table definitions. The final table output will be like below: