ISqlJoinBuilder.LeftJoin(ISqlBuilder sqlBuilder, string alias) Method

.NET Standard 2.x

Uses the LEFT OUTER JOIN operator to join the original table source and the new table source (specified by a subquery generated by an ISqlBuilder object) to create a joined table. You need to specify an alias for the new table source.

Namespace: SnapObjects.Data

Assembly: SnapObjects.Data.dll

Syntax

  ISqlJoinOnBuilder LeftJoin(ISqlBuilder sqlBuilder, string alias);

Parameters

sqlBuilder SnapObjects.Data.ISqlBuilder

An ISqlBuilder object which represents a subquery.

alias System.String

The alias of the new table source specified by the sqlBuilder parameter.

Returns

SnapObjects.Data.ISqlJoinOnBuilder

Returns an ISqlJoinOnBuilder object that can be used to create the condition on which the join is based.

Examples

The following code example joins one table with another using the LeftJoin method.

using SnapObjects.Data;
using System;

namespace Appeon.ApiDoc.ISqlJoinBuilderExamples
{
    public class LeftJoinExample
    {
        private readonly SchoolContext _context;

        public LeftJoinExample(SchoolContext dataContext)
        {
            // Sets data context.
            _context = dataContext;
        }

        public void Example4()
        {
            var sqlQueryBuilder = new SqlQueryBuilder();

            // Defines a query, and gets DepartmentID values and Name values from the "Course" table.
            var sqlBuilder = new SqlQueryBuilder();
            sqlBuilder.Select("DepartmentID")
                      .Select("Title")
                      .From("Course");

            // Gets DepartmentID values and Name values from the "Department" table, and Title values from the "Course" table.
            // Sets the condition to join the "Department" table and the "Course" table: Department.DepartmentID = Course.DepartmentID.
            // Specifies "Course" as the alias of the derived table.
            sqlQueryBuilder
                .Select("Department.DepartmentID")
                .Select("Department.Name")
                .Select("Course.Title")
                .From("Department")
                .LeftJoin(sqlBuilder, "Course")
                .OnRaw("Department.DepartmentID = Course.DepartmentID");

            // Converts to raw SQL for the database corresponding to the data context.
            string sql = sqlQueryBuilder.ToSqlString(_context);

            Console.WriteLine(sql);
            
            /*This code example produces the following output:           
              SELECT
                [Department].[DepartmentID],
                [Department].[Name],
                [Course].[Title]
              FROM [Department]
              Left JOIN (SELECT
                            [DepartmentID],
                            [Title]
                         FROM [Course]) AS [Course]
              ON [Department].[DepartmentID] = [Course].[DepartmentID]
            */
        }
    }
}

Applies to

.NET Standard

2.x