How to drop all tables from a database with one SQL query?

Question

Use the INFORMATION_SCHEMA.TABLES view to get the list of tables. Generate Drop scripts in the select statement and drop it using Dynamic SQL:

DECLARE @sql NVARCHAR(max)=''

SELECT @sql += ' Drop table ' + QUOTENAME(TABLE_SCHEMA) + '.'+ QUOTENAME(TABLE_NAME) + '; '
FROM   INFORMATION_SCHEMA.TABLES
WHERE  TABLE_TYPE = 'BASE TABLE'

Exec Sp_executesql @sql

Sys.Tables Version

DECLARE @sql NVARCHAR(max)=''

SELECT @sql += ' Drop table ' + QUOTENAME(s.NAME) + '.' + QUOTENAME(t.NAME) + '; '
FROM   sys.tables t
       JOIN sys.schemas s
         ON t.[schema_id] = s.[schema_id]
WHERE  t.type = 'U'

Exec sp_executesql @sql

Note: If you have any foreign Keys defined between tables then first run the below query to disable all foreign keys present in your database.

EXEC sp_msforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"

For more information, check here.

If you want to use only one SQL query to delete all tables you can use this:

EXEC sp_MSforeachtable @command1 = "DROP TABLE ?"

This is a hidden Stored Procedure in sql server, and will be executed for each table in the database you're connected.

Note: You may need to execute the query a few times to delete all tables due to dependencies.

Note2: To avoid the first note, before running the query, first check if there foreign keys relations to any table. If there are then just disable foreign key constraint by running the query bellow:

EXEC sp_msforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"

If you don't want to type, you can create the statements with this:

USE Databasename

SELECT  'DROP TABLE [' + name + '];'
FROM    sys.tables

Then copy and paste into a new SSMS window to run it.

You could also use the following script to drop everything, including the following:

• non-system stored procedures
• views
• functions
• foreign key constraints
• primary key constraints
• system_versioning
• tables

https://michaelreichenbach.de/how-to-drop-everything-in-a-mssql-database/

/* Drop all non-system stored procs */
DECLARE @name VARCHAR(128)
DECLARE @SQL VARCHAR(254)

SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] = 'P' AND category = 0 ORDER BY [name])

WHILE @name is not null
BEGIN
    SELECT @SQL = 'DROP PROCEDURE [dbo].[' + RTRIM(@name) +']'
    EXEC (@SQL)
    PRINT 'Dropped Procedure: ' + @name
    SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] = 'P' AND category = 0 AND [name] > @name ORDER BY [name])
END
GO

/* Drop all views */
DECLARE @name VARCHAR(128)
DECLARE @SQL VARCHAR(254)

SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] = 'V' AND category = 0 ORDER BY [name])

WHILE @name IS NOT NULL
BEGIN
    SELECT @SQL = 'DROP VIEW [dbo].[' + RTRIM(@name) +']'
    EXEC (@SQL)
    PRINT 'Dropped View: ' + @name
    SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] = 'V' AND category = 0 AND [name] > @name ORDER BY [name])
END
GO

/* Drop all functions */
DECLARE @name VARCHAR(128)
DECLARE @SQL VARCHAR(254)

SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] IN (N'FN', N'IF', N'TF', N'FS', N'FT') AND category = 0 ORDER BY [name])

WHILE @name IS NOT NULL
BEGIN
    SELECT @SQL = 'DROP FUNCTION [dbo].[' + RTRIM(@name) +']'
    EXEC (@SQL)
    PRINT 'Dropped Function: ' + @name
    SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] IN (N'FN', N'IF', N'TF', N'FS', N'FT') AND category = 0 AND [name] > @name ORDER BY [name])
END
GO

/* Drop all Foreign Key constraints */
DECLARE @name VARCHAR(128)
DECLARE @constraint VARCHAR(254)
DECLARE @SQL VARCHAR(254)

SELECT @name = (SELECT TOP 1 TABLE_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'FOREIGN KEY' ORDER BY TABLE_NAME)

WHILE @name is not null
BEGIN
    SELECT @constraint = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'FOREIGN KEY' AND TABLE_NAME = @name ORDER BY CONSTRAINT_NAME)
    WHILE @constraint IS NOT NULL
    BEGIN
        SELECT @SQL = 'ALTER TABLE [dbo].[' + RTRIM(@name) +'] DROP CONSTRAINT [' + RTRIM(@constraint) +']'
        EXEC (@SQL)
        PRINT 'Dropped FK Constraint: ' + @constraint + ' on ' + @name
        SELECT @constraint = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'FOREIGN KEY' AND CONSTRAINT_NAME <> @constraint AND TABLE_NAME = @name ORDER BY CONSTRAINT_NAME)
    END
SELECT @name = (SELECT TOP 1 TABLE_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'FOREIGN KEY' ORDER BY TABLE_NAME)
END
GO

/* Drop all Primary Key constraints */
DECLARE @name VARCHAR(128)
DECLARE @constraint VARCHAR(254)
DECLARE @SQL VARCHAR(254)

SELECT @name = (SELECT TOP 1 TABLE_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'PRIMARY KEY' ORDER BY TABLE_NAME)

WHILE @name IS NOT NULL
BEGIN
    SELECT @constraint = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'PRIMARY KEY' AND TABLE_NAME = @name ORDER BY CONSTRAINT_NAME)
    WHILE @constraint is not null
    BEGIN
        SELECT @SQL = 'ALTER TABLE [dbo].[' + RTRIM(@name) +'] DROP CONSTRAINT [' + RTRIM(@constraint)+']'
        EXEC (@SQL)
        PRINT 'Dropped PK Constraint: ' + @constraint + ' on ' + @name
        SELECT @constraint = (SELECT TOP 1 CONSTRAINT_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'PRIMARY KEY' AND CONSTRAINT_NAME <> @constraint AND TABLE_NAME = @name ORDER BY CONSTRAINT_NAME)
    END
SELECT @name = (SELECT TOP 1 TABLE_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS WHERE constraint_catalog=DB_NAME() AND CONSTRAINT_TYPE = 'PRIMARY KEY' ORDER BY TABLE_NAME)
END
GO

/* Remove system versioning */
DECLARE @name VARCHAR(128)
DECLARE @SQL VARCHAR(254)

SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] = 'U' AND category = 0 ORDER BY [name])

WHILE @name IS NOT NULL
BEGIN
    IF OBJECTPROPERTY(OBJECT_ID(' + @name + '), 'TableTemporalType') = 2 
        SELECT @SQL = 'ALTER TABLE [dbo].[' + RTRIM(@name) +'] SET (SYSTEM_VERSIONING = OFF); ALTER TABLE [dbo].[' + RTRIM(@name) + '] DROP PERIOD FOR SYSTEM_TIME;'
        EXEC (@SQL)
        PRINT 'System Versioning Disabled for Table: ' + @name
        SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] = 'U' AND category = 0 AND [name] > @name ORDER BY [name])
END
GO

/* Drop all tables */
DECLARE @name VARCHAR(128)
DECLARE @SQL VARCHAR(254)

SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] = 'U' AND category = 0 ORDER BY [name])

WHILE @name IS NOT NULL
BEGIN
    SELECT @SQL = 'DROP TABLE [dbo].[' + RTRIM(@name) +']'
    EXEC (@SQL)
    PRINT 'Dropped Table: ' + @name
    SELECT @name = (SELECT TOP 1 [name] FROM sysobjects WHERE [type] = 'U' AND category = 0 AND [name] > @name ORDER BY [name])
END
GO

The simplest way is to drop the whole database and create it once again:

drop database db_name
create database db_name

That's all.