Скачать или смотреть How to Create an Array of Column Names in BigQuery

Learn how to easily extract column names from a table in BigQuery and create an array for further use in your projects.
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Creating an Array of Column Names in BigQuery

When working with data in BigQuery, you may encounter situations where you need to dynamically access or manipulate the names of the columns in a particular table. For instance, you may want to create an array that contains all the column names from your table for further analysis or processing. This guide will walk you through the steps to achieve this efficiently.

The Challenge

Suppose you have a table named table1 within a database called Books1. You realize that simply querying the column names isn't sufficient; you want to work with these names programmatically. Here's where the challenge lies: How do you convert the list of column names into an array for later use?

Solution Overview

To create an array of column names in BigQuery, you can utilize the ARRAY_AGG function. This function aggregates values into an array, allowing you to collect the column names into a structured format that you can access later on.

Step-by-step Guide

Declare Your Array Variable: Start by declaring an array variable that will hold the column names.

Set the Array Variable: Use a query with the ARRAY_AGG function to populate your declared array with the column names from table1.

Step 1: Declare Your Array Variable

You need to declare an array variable that will hold the names of the columns. The syntax for declaring an array in BigQuery is straightforward:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Set the Array Variable

Next, you'll want to assign values to your array variable using a query that selects the column names. Here's the complete code to set up the array with the column names from table1:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

ARRAY_AGG(column_name): This function collects all column names that match the criteria into a single array.

FROM Books1.INFORMATION_SCHEMA.COLUMNS: This specifies the metadata table that contains the information about your table's columns.

WHERE TABLE_NAME = 'table1': This clause ensures you're only getting the column names for the targeted table.

Summary

By following the steps outlined above, you can conveniently create an array of column names in BigQuery. This tool can be incredibly useful when you want to iterate over each column or dynamically generate queries based on your schema.

Final Thoughts

Understanding how to manage your database schema dynamically can save time and improve the efficiency of your data analysis tasks. With the method described, you can create your own array of column names and use it for various applications within your BigQuery projects.

By incorporating these practices into your workflow, you not only streamline your processes but also gain more control over your data management tasks in Google Cloud Platform's BigQuery.