BigQuery is a powerful and fully-managed data warehousing solution provided by Google Cloud Platform (GCP). It allows users to easily analyze large amounts of data using SQL-like query language and perform various data operations such as filtering, aggregation, and joining. One of the key features of BigQuery is its ability to handle large datasets, making it a popular choice for data analysts, engineers, and scientists.
One of the most common tasks in BigQuery is casting data types. Casting refers to the process of converting one data type to another. For example, casting a string to a date, or a timestamp to an integer. In this article, we will explore how to cast data types in BigQuery with code examples.
Before we begin, it's important to note that BigQuery supports several data types such as INTEGER, FLOAT, BOOLEAN, DATE, TIMESTAMP, and STRING. Each data type has its own set of functions and operators that can be used to perform various operations.
Casting to DATE
In BigQuery, the DATE data type stores a calendar date in the format YYYY-MM-DD. To cast a string or timestamp to a date, we can use the DATE() function. For example, the following query converts a string '2022-01-01' to a date:
SELECT DATE('2022-01-01') as date;
This query will return the date '2022-01-01'.
We can also convert a timestamp to a date using the DATE() function. For example, the following query converts a timestamp '2022-01-01 10:00:00' to a date:
SELECT DATE(TIMESTAMP '2022-01-01 10:00:00') as date;
This query will return the date '2022-01-01'.
Casting to TIMESTAMP
In BigQuery, the TIMESTAMP data type stores a date and time value in the format YYYY-MM-DD HH:MM:SS. To cast a string or date to a timestamp, we can use the TIMESTAMP() function. For example, the following query converts a string '2022-01-01 10:00:00' to a timestamp:
SELECT TIMESTAMP('2022-01-01 10:00:00') as timestamp;
This query will return the timestamp '2022-01-01 10:00:00'.
We can also convert a date to a timestamp using the TIMESTAMP() function. For example, the following query converts a date '2022-01-01' to a timestamp:
SELECT TIMESTAMP(DATE '2022-01-01') as timestamp;
This query will return the timestamp '2022-01-01 00:00:00'.
Casting to INTEGER
In BigQuery, the INTEGER data type stores a whole number value. To cast a string or float to an integer, we can use the INTEGER() function. For example, the following query converts a string '10' to an integer:
SELECT INTEGER('10') as integer;
This query will return the integer 10.
We can also convert a float to an integer using the INTEGER() function. For example, the following query converts a float 10.5 to an integer:
Casting to FLOAT
In BigQuery, the FLOAT data type stores a decimal number value. To cast a string or integer to a float, we can use the FLOAT() function. For example, the following query converts a string '10.5' to a float:
SELECT FLOAT('10.5') as float_value;
This query will return the float value 10.5.
We can also convert an integer to a float using the FLOAT() function. For example, the following query converts an integer 10 to a float:
SELECT FLOAT(10) as float_value;
This query will return the float value 10.0.
Casting to BOOLEAN
In BigQuery, the BOOLEAN data type stores a true or false value. To cast a string to a boolean, we can use the BOOL() function. For example, the following query converts a string 'true' to a boolean:
SELECT BOOL('true') as boolean_value;
This query will return the boolean value true.
It's important to note that the BOOL() function only accepts strings 'true' and 'false' as input. If any other value is passed, it will return null.
Casting to STRING
In BigQuery, the STRING data type stores a text value. To cast a date, timestamp or any other datatype to a string, we can use the STRING() function. For example, the following query converts a date '2022-01-01' to a string:
SELECT STRING(DATE '2022-01-01') as string_value;
This query will return the string value '2022-01-01'.
It's also possible to cast timestamp, integer, float, boolean etc to string
SELECT STRING(TIMESTAMP '2022-01-01 10:00:00') as timestamp_string;
SELECT STRING(10) as integer_string;
SELECT STRING(10.5) as float_string;
SELECT STRING(TRUE) as boolean_string;
These queries will return the respective values as string.
Casting data types in BigQuery can be useful when working with different data formats or when performing certain operations that require a specific data type. The functions and operators discussed in this article provide a simple and straightforward way to cast data types in BigQuery. It's important to be aware of the data type of the values you're working with and to use the appropriate function or operator when casting.
## Popular questions
1. What function can be used to cast a string to a date in BigQuery?
Answer: The DATE() function can be used to cast a string to a date in BigQuery.
2. Can an integer be cast to a date in BigQuery?
Answer: No, an integer cannot be cast to a date in BigQuery. The DATE() function only accepts strings in the format 'yyyy-mm-dd' as input.
3. How can a timestamp be cast to a date in BigQuery?
Answer: A timestamp can be cast to a date in BigQuery by using the DATE() function on the timestamp column. For example, the query `SELECT DATE(timestamp_column) as date_column` will return the date portion of the timestamp in the format 'yyyy-mm-dd'.
4. What is the format of the string that can be used to cast to a timestamp in BigQuery?
Answer: The format of the string that can be used to cast to a timestamp in BigQuery is 'yyyy-mm-dd hh:mm:ss' or 'yyyy-mm-dd hh:mm:ss.sss'
5. Can a float be cast to a date in BigQuery?
Answer: No, a float cannot be cast to a date in BigQuery. The DATE() function only accepts strings in the format 'yyyy-mm-dd' as input, and cannot process a float value.
### Tag
Conversion
