Last_name = 'Rice' Code language: SQL (Structured Query Language) ( sql ) 3) Using the WHERE clause with the OR operator example The following example finds customers whose first name and last name are Jamie and rice by using the AND logical operator to combine two Boolean expressions: SELECT The following statement uses the WHERE clause customers whose first names are Jamie: SELECTįirst_name = 'Jamie' Code language: SQL (Structured Query Language) ( sql ) 2) Using WHERE clause with the AND operator example 1) Using WHERE clause with the equal ( =) operator example We will use the customer table from the sample database for demonstration. Let’s practice with some examples of using the WHERE clause. Return true if a value is between a range of values Return true if a value matches any value in a list To form the condition in the WHERE clause, you use comparison and logical operators: Operator If you use column aliases in the SELECT clause, you cannot use them in the WHERE clause.īesides the SELECT statement, you can use the WHERE clause in the UPDATE and DELETE statement to specify rows to be updated or deleted. PostgreSQL evaluates the WHERE clause after the FROM clause and before the SELECT and ORDER BY clause: In other words, only rows that cause the condition evaluates to true will be included in the result set. The query returns only rows that satisfy the condition in the WHERE clause. It can be a boolean expression or a combination of boolean expressions using the AND and OR operators. The condition must evaluate to true, false, or unknown. The WHERE clause uses the condition to filter the rows returned from the SELECT clause. The WHERE clause appears right after the FROM clause of the SELECT statement. ORDER BY sort_expression Code language: SQL (Structured Query Language) ( sql ) The syntax of the PostgreSQL WHERE clause is as follows: SELECT select_list To select rows that satisfy a specified condition, you use a WHERE clause. The SELECT statement returns all rows from one or more columns in a table. Offset specify the number of records to skip before starting to return the records db.Limit( 3).Find(&users)ĭb.Limit( 10).Find(&users1).Limit( -1).Summary: in this tutorial, you will learn how to use PostgreSQL WHERE clause to filter rows returned by a SELECT statement. Limit specify the max number of records to retrieve SELECT * FROM users ORDER BY FIELD(id,1,2,3) When the destination object has a primary value, the primary key will be used to build the condition, for example: var user = User, If the primary key is a string (for example, like a uuid), the query will be written as follows: db.First(&user, "id = ?", "1b74413f-f3b8-409f-ac47-e8c062e3472a") SELECT * FROM users WHERE id IN (1,2,3) When working with strings, extra care needs to be taken to avoid SQL Injection check out Security section for details. Objects can be retrieved using primary key by using Inline Conditions if the primary key is a number. SELECT * FROM `languages` ORDER BY `languages`.`code` LIMIT 1 no primary key defined, results will be ordered by first field (i.e., `Code`) works because model is specified using `db.Model()` SELECT * FROM `users` ORDER BY `users`.`id` LIMIT 1 works because destination struct is passed in Additionally, if no primary key is defined for relevant model, then the model will be ordered by the first field. They only work when a pointer to the destination struct is passed to the methods as argument or when the model is specified using db.Model(). The First and Last methods will find the first and last record (respectively) as ordered by primary key. Using Find without a limit for single object db.Find(&user) will query the full table and return only the first object which is not performant and nondeterministic If you want to avoid the ErrRecordNotFound error, you could use Find like db.Limit(1).Find(&user), the Find method accepts both struct and slice data Result.RowsAffected // returns count of records foundĮrrors.Is(result.Error, gorm.ErrRecordNotFound) SELECT * FROM users ORDER BY id DESC LIMIT 1 Get last record, ordered by primary key desc SELECT * FROM users ORDER BY id LIMIT 1 Get the first record ordered by primary key GORM provides First, Take, Last methods to retrieve a single object from the database, it adds LIMIT 1 condition when querying the database, and it will return the error ErrRecordNotFound if no record is found.
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