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MySQLi Articles
Page 263 of 341
Does it make sense to use "LIMIT 1" in a query "SELECT 1 ..."?
Yes, you can use LIMIT 1 with SELECT1.Suppose, you are using SELECT 1 and your table has billions of records. In this case, it will print 1 billion times.The syntax of SELECT 1 is as follows −SELECT 1 FROM yourTableName;Suppose, you are using LIMIT 1 and your table has billions of records. This case, it will print 1 only once.The syntax of SELECT 1 with LIMIT 1 is as follows −SELECT 1 FROM yourTableName LIMIT 1;To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table Select1AndLimit1Demo -> ...
Read MoreDisplay the warning message when a FLOAT value is inserted into DECIMAL in MySQL?
You can create a temporary table with data type DECIMAL to get a warning when a float value is inserted into an int column. Display the same warning using SHOW WARNINGS.Let us create a table to understand. The query is as follows to create a table.mysql> create temporary table WarningDemo -> ( -> Value DECIMAL -> ); Query OK, 0 rows affected (0.13 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into WarningDemo values(9.80); Query OK, 1 row affected, 1 warning (0.03 sec)Here we are getting a warning. Let ...
Read MoreSelect query using MySQL IN() and avoid sorting in it
Using IN() sorts the result for the specific field. To avoid this, use ORDER BY and FIND_IN_SET() for the field.To understand the find_in_set(), let us create a table. The query to create a table is as follows −mysql> create table ProductStock -> ( -> ProductId int, -> ProductName varchar(20), -> ProductQuantity int, -> ProductPrice float -> ); Query OK, 0 rows affected (0.79 sec)Now you can insert some records in the table using insert command. The query is as follows −mysql> insert into ProductStock values(1, 'Product-101', 10, 500.56); Query OK, 1 row affected (0.20 ...
Read MoreCreate an aggregate checksum of a column in MySQL
You can use CRC32 checksum for this. The syntax is as follows −SELECT SUM(CRC32(yourColumnName)) AS anyAliasName FROM yourTableName;To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table CRC32Demo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> UserId varchar(20) -> ); Query OK, 0 rows affected (0.67 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into CRC32Demo(UserId) values('USER-1'); Query OK, 1 row affected (0.38 sec) mysql> insert into CRC32Demo(UserId) values('USER-123'); Query OK, 1 row ...
Read MoreExtract tuples with specified common values in another column in MySQL?
To extract tuples with specified common values, use the following syntax −SELECT DISTINCT aliasName.yourColumnName1, aliasName.yourColumnName2, aliasName1.yourColumnName 1, aliasName1.yourColumnName2 FROM yourTableName aliasName INNER JOIN yourTableName aliasName1 ON aliasName.yourColumnName1 = aliasName1.yourColumnName1 WHERE aliasName.yourColumnName2 = 'value1' AND aliasName1.yourColumnName2 = 'value2';To understand the above syntax, let us create a table. The query to create a table is as follows −mysql> create table extractTuples -> ( -> Id int, -> Name varchar(20), -> Comments text -> ); Query OK, 0 rows affected (0.77 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into ...
Read MoreHow to write a MySQL "LIMIT" in SQL Server?
You need to use TOP(1) in SQL Server. The syntax is as follows −SELECT TOP(1) *FROM yourTableName WHERE yourCondition;To understand the above syntax, let us create a table. The query to create a table is as follows −create table TopDemoInSQLServer ( Id int, Name varchar(10) );The snapshot of creation of table is as follows −Insert some records in the table using insert command. The query is as follows −insert into TopDemoInSQLServer values(10, 'John'); insert into TopDemoInSQLServer values(14, 'Carol'); insert into TopDemoInSQLServer values(1, 'Sam'); insert into TopDemoInSQLServer values(11, 'Bob'); insert into TopDemoInSQLServer values(18, 'David'); insert into TopDemoInSQLServer values(20, 'Sam');The ...
Read MoreHow to work with one database connection object in the entire Java-MySQL application?
Use the singleton design pattern. Here is the Java code that returns a single object −ConnectDatabase.javaimport java.sql.Connection; import java.sql.DriverManager; public class ConnectDatabase { static Connection conn = null; public static Connection getConnection() { if (conn != null) return conn; String database = "test"; String Username = "root"; String password = "123456"; return getConnection(database, Username, password); } private static Connection getConnection(String databaseName, String UserName, String password) { try { Class.forName("com.mysql.jdbc.Driver"); conn ...
Read MoreHow can I set a MySQL database to use MyISAM by default?
To set the default storage engine, use the following syntax −set @@default_storage_engine = ’yourEngineType’;Now implement the above syntax to set the default engine to MyISAM. The query is as follows −mysql> set @@default_storage_engine = 'MyISAM'; Query OK, 0 rows affected (0.05 sec)Now you can check the default engine type with the help of SELECT statement. The query is as follows −mysql> select @@default_storage_engine;The following is the output displaying the engine as MyISAM −+--------------------------+ | @@default_storage_engine | +--------------------------+ | MyISAM | +--------------------------+ 1 ...
Read MoreDoes MySQL support table inheritance?
MySQL uses foreign key constraint instead of inheritance. MySQL does not support table inheritance.You can achieve the same with the help of foreign key constraint. Let us create a table and use the foreign key constraint. The query to create the first table is as follows −mysql> create table Parent_Table -> ( -> ParentId int, -> PRIMARY KEY(ParentId) -> ); Query OK, 0 rows affected (3.59 sec)Now create the second table. The query to create the second table is as follows −mysql> create table Child_Table ...
Read MoreHow do I get the average string length in MySQL?
To get the average string length in MySQL, we will work around a query that gets rows from 1 to 10 and displays the result.Let us first create a table. The query to create a table is as follows −mysql> create table AverageString -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value varchar(20) -> ); Query OK, 0 rows affected (0.66 sec)Insert some records in the table using insert command. The query is as follows −mysql> insert into AverageString(Value) values('MySQL Query'); Query OK, 1 row ...
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