How Can I Efficiently Create a Temporary Table in SQL to Filter Data?

Creating Temporary Tables in SQL Using CREATE TABLE AS

When aiming to create a temporary table to select data based on a specific criterion, such as the register_type in your provided query, the correct syntax requires the use of the CREATE TABLE AS statement. In your case, the corrected query would be:

CREATE TEMP TABLE temp1 AS
SELECT
    egauge.dataid,
    egauge.register_type,
    egauge.timestamp_localtime,
    egauge.read_value_avg
FROM
    rawdata.egauge
WHERE
    register_type LIKE '%gen%'
ORDER BY
    dataid, timestamp_localtime;

Explanation:

Unlike the CREATE TABLE statement, CREATE TABLE AS performs both table creation and data insertion simultaneously. It allows you to create a temporary table that is a snapshot of the data at the time of creation. This temporary table is visible only within the current session and disappears automatically once the session ends.

Advantages of CREATE TABLE AS:

• Efficient: It is a faster and more efficient way to create a temporary table compared to using other methods like SELECT INTO.
• Portable: It is part of the SQL standard and works across different database systems.
• Flexible: It allows for data filtering and sorting during table creation.

When ALTERNATE SYNTAXES WOULD BE USED:

• CREATE VIEW: When you want a dynamic result set that reflects real-time changes in the underlying tables.
• SELECT INTO: This is not typically recommended for creating temporary tables. However, it can be used for quick, one-time data aggregation.
• CREATE TABLE LIKE: This syntax only creates a table with the same structure as the existing table without copying any data.

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