ISqlWhereBuilder.WhereExists(ISqlBuilder sqlBuilder) Method

.NET Standard 2.x

Creates a WHERE clause, and adds a search condition to the WHERE clause. Uses EXISTS to test for the existence of the record returned from a subquery.

Namespace: SnapObjects.Data

Assembly: SnapObjects.Data.dll

Syntax

  ISqlWhereAndOr WhereExists(ISqlBuilder sqlBuilder);

Parameters

sqlBuilder SnapObjects.Data.ISqlBuilder

An ISqlBuilder object which represents a SQL subquery on the right of the EXISTS operator.

Returns

SnapObjects.Data.ISqlWhereAndOr

Returns the ISqlWhereAndOr object which can be used to add more search conditions to the current WHERE clause.

Examples

The following code example uses the WhereExists method to specify that the "Title" value of the "Course" table must exist in the result set of the subquery.

using SnapObjects.Data;
using System;

namespace Appeon.ApiDoc.ISqlWhereBuilderExamples
{
    public class WhereExistsExample
    {
        private readonly SchoolContext _context;

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

        public void Example()
        {

            // Declares SqlQueryBuilder.
            var sqlbuilder = new SqlQueryBuilder();

            // Defines a subquery.
            var deptsql = new SqlQueryBuilder();
            deptsql.Select("DepartmentID")
                .From("Department", "d")
                .Where("d.DepartmentID", "c.DepartmentID")
                .AndWhere("d.Name", SqlBuilder.Parameter<string>("id"));

            // Defines a SQL statement, and specifies the WHERE EXIST condition:
            // the data exists in the result set of the subquery.
            sqlbuilder.Select("Title")
                .From("Course", "c")
                .WhereExists(deptsql);

            string sql = sqlbuilder.ToSqlString(_context);

            Console.WriteLine(sql);

            /*This code produces the following output:

            SELECT
            [Title]
            FROM [Course] AS [c]
            WHERE ( EXISTS (SELECT
            [DepartmentID]
            FROM [Department] AS [d]
            WHERE ([d].[DepartmentID] = [c].[DepartmentID]
            AND [d].[Name] = @id)))
           */
        }
    }
}

Applies to

.NET Standard

2.x