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As needed, you can insert custom SQL statements as part of the data import process. These custom SQL statements allow you to pre-filter the rows and columns of relational source data within data within the database, where performance is faster. This query method can also be used for wider operations on relational sources from within within the
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Limitations
General
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All queries are blindly executed. It is your responsibility to ensure that they are appropriate. Queries like |
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NOTE: Column names in custom SQL statements are case-sensitive. Case mismatches between SQL statement and your datasource can cause jobs to fail. |
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SQL statements are stored as part of the query instance for the object. If the same query is being made across multiple users using private connections, the SQL must be shared and entered by individual users.
Info NOTE: If a dataset created from custom SQL is shared, collaborators are not permitted to edit the custom SQL.
Each statement must be terminated with a semi-colon (
;) and a newline:Code Block SELECT * FROM myDB.myTable;
SQL statements must be valid for the syntax of the target relational system.
- If you modify the custom SQL statement when reading from a source, all samples generated based on the previous SQL are invalidated.
Declared variables are not supported.
- Common Table Expressions (CTEs) are not supported.
- For each SQL statement, all columns must have an explicit name. Example:
Function references such as:
Code Block UPPER(col)
Must be specified as:
Code Block UPPER(col) as col_name
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- In the Library page, click Import Data.
- In the Import Data page, select a connection.
- Within your source, locate the table from which you wish to import. Do not select the table.
Click the Preview icon to review the columns in the dataset.
Tip Tip: You may wish to copy the database, table name, and column names to a text editor to facilitate generating your SQL statement.
Click Create Dataset with SQL. Enter or paste your SQL statement.
Warning Through the custom SQL interface, it is possible to enter SQL statements that can delete data, change table schemas, or otherwise corrupt the targeted database. Please use this feature with caution.
Info NOTE: If this button is disabled and you have enabled the custom SQL feature, the connection that you are using may lack credentials. Please review the connection definition.
D caption Create Dataset with SQL dialog
To test the SQL, click Validate SQL. For details, see below.
To apply the SQL to the import process, click Create Dataset.
The customized source is added to the right panel. To re-edit, click Custom SQL.
Complete the other steps to define your imported dataset.
When the data is imported, it is altered or filtered based on your SQL statement.
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