SOQL and SOSL Reference

Introduction to SOQL and SOSL
Salesforce Object Query Language (SOQL)
Typographical Conventions in This Document
Quoted String Escape Sequences
Reserved Characters
Alias Notation
SOQL SELECT Syntax
SELECT
TYPEOF
USING SCOPE
WHERE
WITH
GROUP BY
HAVING
ORDER BY
LIMIT
OFFSET
FOR VIEW and and FOR REFERENCE
UPDATE
SET OPTIONS
FOR UPDATE
SOQL SELECT Examples
SOQL SELECT Functions
Relationship Queries
Change the Batch Size in Queries
SOQL Object Limits and Limitations
Syndication Feed SOQL and Mapping Syntax
Location-Based SOQL Queries
Considerations for Querying Currency Data Using SOQL
Salesforce Object Search Language (SOSL)
PDF

FOR UPDATE

In Apex, you can use FOR UPDATE to lock sObject records while they’re being updated in order to prevent race conditions and other thread safety problems.

While an sObject record is locked, no other client or user is allowed to make updates either through code or the Salesforce user interface. The client locking the records can perform logic on the records and make updates with the guarantee that the locked records won’t be changed by another client during the lock period. The lock gets released when the transaction completes.

You can’t use the ORDER BY clause in any SOQL query that uses locking.

Note

To lock a set of sObject records in Apex, embed the keywords FOR UPDATE after any inline SOQL statement. This example queries for two accounts and also locks the accounts that are returned.
1Account [] accts = [SELECT Id FROM Account LIMIT 2 FOR UPDATE];

Use care when setting locks in your Apex code. For details, see Locking Records in the Apex Developer Guide.

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