# Differences in scanning a table
<a name="SQLtoNoSQL.ReadData.Scan"></a>

In SQL, a `SELECT` statement without a `WHERE` clause will return every row in a table. In Amazon DynamoDB, the `Scan` operation does the same thing. In both cases, you can retrieve all of the items or just some of them.

Whether you are using a SQL or a NoSQL database, scans should be used sparingly because they can consume large amounts of system resources. Sometimes a scan is appropriate (such as scanning a small table) or unavoidable (such as performing a bulk export of data). However, as a general rule, you should design your applications to avoid performing scans. For more information, see [Querying tables in DynamoDB](Query.md).

**Note**  
Doing a bulk export also creates at least 1 file per partition. All of the items in each file are from that particular partition's hashed keyspace.

**Topics**
+ [Scanning a table with SQL](#SQLtoNoSQL.ReadData.Scan.SQL)
+ [Scanning a table in DynamoDB](#SQLtoNoSQL.ReadData.Scan.DynamoDB)

## Scanning a table with SQL
<a name="SQLtoNoSQL.ReadData.Scan.SQL"></a>

When using SQL you can scan a table and retrieve all of its data by using a `SELECT` statement without specifying a `WHERE` clause. You can request one or more columns in the result. Or you can request all of them if you use the wildcard character (\$1).

The following are examples of using a `SELECT` statement.

```
/* Return all of the data in the table */
SELECT * FROM Music;
```

```
/* Return all of the values for Artist and Title */
SELECT Artist, Title FROM Music;
```

## Scanning a table in DynamoDB
<a name="SQLtoNoSQL.ReadData.Scan.DynamoDB"></a>

In Amazon DynamoDB, you can use either the DynamoDB API or [PartiQL](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/ql-reference.html) (a SQL-compatible query language) to perform a scan on a table.

------
#### [ DynamoDB API ]

With the DynamoDB API, you use the `Scan` operation to return one or more items and item attributes by accessing every item in a table or a secondary index.

```
// Return all of the data in the table
{
    TableName:  "Music"
}
```

```
// Return all of the values for Artist and Title
{
    TableName:  "Music",
    ProjectionExpression: "Artist, Title"
}
```

The `Scan` operation also provides a `FilterExpression` parameter, which you can use to discard items that you do not want to appear in the results. A `FilterExpression` is applied after the scan is performed, but before the results are returned to you. (This is not recommended with large tables. You are still charged for the entire `Scan`, even if only a few matching items are returned.)

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#### [ PartiQL for DynamoDB ]

With PartiQL, you perform a scan by using the `ExecuteStatement` operation to return all the contents for a table using the `Select` statement.

```
SELECT AlbumTitle, Year, Price
FROM Music
```

Note that this statement will return all items for in the Music table. 

For code examples using `Select` and `ExecuteStatement`, see [PartiQL select statements for DynamoDB](ql-reference.select.md).

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