How to create a yes/no boolean field in SQL server?

The `BIT` datatype is generally used to store `boolean` values (`0` for `false`, `1` for `true`).

The equivalent is a `BIT` field.

In `SQL` you use `0` and `1` to set a bit field (just as a yes/no field in Access). In Management Studio it displays as a false/true value (at least in recent versions).

When accessing the database through ASP.NET it will expose the field as a boolean value.

You can use **[BIT][1] type** which can have `1` or `0`, or also `NULL` if `NULL` is allowed.

**[BIT][1] type** converts:
- Any integer values except `0` to `1`.
- Any integer string values except `"0"` to `1`.
- `"0"` to `0`.

Then, you can create a table with **[BIT][1] type** as shown below:

```lang-none
CREATE TABLE doctor (
id INT IDENTITY,
name NVARCHAR(50),
on_call BIT, -- Here
PRIMARY KEY(id)
)
GO
```

Then, insert rows as shown below:

```mssql
INSERT INTO doctor
VALUES ("John", 1), ("Tom", 0), ("Lisa", "-23"), ("Kai", "0"), ("Bob", NULL)
GO
```

```lang-none
1> SELECT * FROM doctor
2> GO
id name on_call
-- ---- -------
1 John 1 <- 1
2 Tom 0 <- 0
3 Lisa 1 <- "-23"
4 Kai 0 <- "0"
5 Bob NULL <- NULL
```


[1]:

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***Below the List of database where what type of datatype is use for Boolean***


-> **Oracle** -> Number(1)

-> **SQL Server** -> BIT

-> **MySql** -> BIT or TINYINT

->**postgreSQL** -> boolean


I hope this is really helpful thanks.