Splunk SPL for SQL users

This is not a perfect mapping between SQL and Splunk Search Processing Language (SPL), but if you are familiar with SQL, this quick comparison might be helpful as a jump-start into using the search commands.

Concepts

The Splunk platform does not store data in a conventional database. Rather, it stores data in a distributed, non-relational, semi-structured database with an implicit time dimension. Relational databases require that all table columns be defined up-front and they do not automatically scale by just plugging in new hardware. However, there are analogues to many of the concepts in the database world.

Database Concept	Splunk Concept	Notes
SQL query	Splunk search	A Splunk search retrieves indexed data and can perform transforming and reporting operations. Results from one search can be "piped", or transferred, from command to command, to filter, modify, reorder, and group your results.
table/view	search results	Search results can be thought of as a database view, a dynamically generated table of rows, with columns.
index	index	All values and fields are indexed by Splunk software, so there is no need to manually add, update, drop, or even think about indexing columns. Everything can be quickly retrieved automatically.
row	result/event	A result in a Splunk search is a list of fields (i.e., column) values, corresponding to a table row. An event is a result that has a timestamp and raw text. Typically an event is a record from a log file, such as: 173.26.34.223 - - [01/Jul/2009:12:05:27 -0700] "GET /trade/app?action=logout HTTP/1.1" 200 2953
column	field	Fields are returned dynamically from a search, meaning that one search might return a set of fields, while another search might return another set. After teaching Splunk software how to extract more fields from the raw underlying data, the same search will return more fields than it previously did. Fields are not tied to a datatype.
database/schema	index/app	A Splunk index is a collection of data, somewhat like a database has a collection of tables. Domain knowledge of that data, how to extract it, what reports to run, etc, are stored in a Splunk application.

From SQL to Splunk SPL

SQL is designed to search relational database tables which are comprised of columns. SPL is designed to search events, which are comprised of fields. In SQL, you often see examples that use "mytable" and "mycolumn". In SPL, you will see examples that refer to "fields". In these examples, the "source" field is used as a proxy for "table". In Splunk software, "source" is the name of the file, stream, or other input from which a particular piece of data originates, for example /var/log/messages or UDP:514.

When translating from any language to another, often the translation is longer because of idioms in the original language. Some of the Splunk search examples shown below could be more concise and more efficient, but for parallelism and clarity, the SPL table and field names are kept the same as the SQL example.

• SPL searches rarely need the FIELDS command to filter out columns because the user interface provides a more convenient method for filtering. The FIELDS command is used in the SPL examples for parallelism.
• With SPL, you never have to use the AND operator in Boolean searches, because AND is implied between terms. However when you use the AND or OR operators, they must be specified in uppercase.
• SPL commands do not need to be specified in uppercase. In the these SPL examples, the commands are specified in uppercase for easier identification and clarity.
• Although some SPL commands loosely correspond to specific SQL commands as shown in the following table, your SPL searches might not produce the desired results if you "think in SQL." For this reason, avoid directly translating from SQL to SPL when you design your searches. See About the search language in the Search Manual for an overview of SPL.

SQL command	SQL example	Splunk SPL example
SELECT *	SELECT * FROM mytable	source=mytable
WHERE	SELECT * FROM mytable WHERE mycolumn=5	source=mytable mycolumn=5
SELECT	SELECT mycolumn1, mycolumn2 FROM mytable	source=mytable | FIELDS mycolumn1, mycolumn2
AND/OR	SELECT * FROM mytable WHERE (mycolumn1="true" OR mycolumn2="red") AND mycolumn3="blue"	source=mytable AND (mycolumn1="true" OR mycolumn2="red") AND mycolumn3="blue" Note: The AND operator is implied in SPL and does not need to be specified. For this example you could also use: source=mytable (mycolumn1="true" OR mycolumn2="red") mycolumn3="blue"
AS (alias)	SELECT mycolumn AS column_alias FROM mytable	source=mytable | RENAME mycolumn as column_alias | FIELDS column_alias
BETWEEN	SELECT * FROM mytable WHERE mycolumn BETWEEN 1 AND 5	source=mytable mycolumn>=1 mycolumn<=5
GROUP BY	SELECT mycolumn, avg(mycolumn) FROM mytable WHERE mycolumn=value GROUP BY mycolumn	source=mytable mycolumn=value | STATS avg(mycolumn) BY mycolumn | FIELDS mycolumn, avg(mycolumn) Several commands use a by-clause to group information, including chart, rare, sort, stats, and timechart.
HAVING	SELECT mycolumn, avg(mycolumn) FROM mytable WHERE mycolumn=value GROUP BY mycolumn HAVING avg(mycolumn)=value	source=mytable mycolumn=value | STATS avg(mycolumn) BY mycolumn | SEARCH avg(mycolumn)=value | FIELDS mycolumn, avg(mycolumn)
LIKE	SELECT * FROM mytable WHERE mycolumn LIKE "%some text%"	source=mytable mycolumn="*some text*" Note: The most common search in Splunk SPL is nearly impossible in SQL - to search all fields for a substring. The following SPL search returns all rows that contain "some text" anywhere: source=mytable "some text"
ORDER BY	SELECT * FROM mytable ORDER BY mycolumn desc	source=mytable | SORT -mycolumn In SPL you use a negative sign ( - ) in front of a field name to sort in descending order.
SELECT DISTINCT	SELECT DISTINCT mycolumn1, mycolumn2 FROM mytable	source=mytable | DEDUP mycolumn1, mycolumn2 | FIELDS mycolumn1, mycolumn2
SELECT TOP	SELECT TOP(5) mycolum1, mycolum2 FROM mytable1 WHERE mycolum3 = "bar" ORDER BY mycolum1 mycolum2	Source=mytable1 mycolum3="bar" | FIELDS mycolum1 mycolum2 | SORT mycolum1 mycolum2 | HEAD 5
INNER JOIN	SELECT * FROM mytable1 INNER JOIN mytable2 ON mytable1.mycolumn= mytable2.mycolumn	index=myIndex1 OR index=myIndex2 | stats values(*) AS * BY myField Note: There are two other methods to join tables: Use the lookup command to add fields from an external table: ... | LOOKUP myvaluelookup mycolumn OUTPUT myoutputcolumn Use a subsearch: source=mytable1 [SEARCH source=mytable2 mycolumn2=myvalue | FIELDS mycolumn2] If the columns that you want to join on have different names, use the rename command to rename one of the columns. For example, to rename the column in mytable2: source=mytable1 | JOIN type=inner mycolumn [ SEARCH source=mytable2 | RENAME mycolumn2 AS mycolumn] To rename the column in myindex1: index=myIndex1 OR index=myIndex2 | rename myfield1 as myField | stats values(*) AS * BY myField You can rename a column regardless of whether you use the search command, a lookup, or a subsearch.
LEFT (OUTER) JOIN	SELECT * FROM mytable1 LEFT JOIN mytable2 ON mytable1.mycolumn= mytable2.mycolumn	source=mytable1 | JOIN type=left mycolumn [SEARCH source=mytable2]
SELECT INTO	SELECT * INTO new_mytable IN mydb2 FROM old_mytable	source=old_mytable | EVAL source=new_mytable | COLLECT index=mydb2 Note: COLLECT is typically used to store expensively calculated fields back into your Splunk deployment so that future access is much faster. This current example is atypical but shown for comparison to the SQL command. The source will be renamed orig_source
TRUNCATE TABLE	TRUNCATE TABLE mytable	source=mytable | DELETE
INSERT INTO	INSERT INTO mytable VALUES (value1, value2, value3,....)	Note: see SELECT INTO. Individual records are not added via the search language, but can be added via the API if need be.
UNION	SELECT mycolumn FROM mytable1 UNION SELECT mycolumn FROM mytable2	source=mytable1 | APPEND [SEARCH source=mytable2] | DEDUP mycolumn
UNION ALL	SELECT * FROM mytable1 UNION ALL SELECT * FROM mytable2	source=mytable1 | APPEND [SEARCH source=mytable2]
DELETE	DELETE FROM mytable WHERE mycolumn=5	source=mytable1 mycolumn=5 | DELETE
UPDATE	UPDATE mytable SET column1=value, column2=value,... WHERE some_column=some_value	Note: There are a few things to think about when updating records in . First, you can just add the new values to your Splunk deployment (see INSERT INTO) and not worry about deleting the old values, because Splunk software always returns the most recent results first. Second, on retrieval, you can always de-duplicate the results to ensure only the latest values are used (see SELECT DISTINCT). Finally, you can actually delete the old records (see DELETE).

See also

• Understanding SPL syntax