ArcGIS Pro 2.6 API Reference Guide
Tables Property (QueryDef)
Example 

ArcGIS.Core.Data Namespace > QueryDef Class : Tables Property
Gets or sets a comma (,) delimited string of tables for use in the query.
Syntax
public string Tables {get; set;}
Public Property Tables As String
Remarks
The string may contain the name of a single table (querying from one single table in the geodatabase) or a list of table names when used in a join (querying from more than one tables in the geodatabase). For example, to perform an inner join against two tables: QueryDef queryDef = new QueryDef() { Tables = "Parcels INNER JOIN Owners ON PROPERTY_I = PROPERTY_ID", PostfixClause = "ORDER BY OWNER_NAME" };
Example
QueryDef queryDef = new QueryDef()
{
  Tables        = "Parcels INNER JOIN Owners ON PROPERTY_I = PROPERTY_ID", 
  PostfixClause = "ORDER BY OWNER_NAME"    
};
Requirements

Target Platforms: Windows 10, Windows 8.1, Windows 7

See Also

Reference

QueryDef Class
QueryDef Members