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Articles on Trending Technologies
Technical articles with clear explanations and examples
MySQL SELECT to skip first N results?
To skip records in MySQL SELECT, use OFFSET. Let us first create a table−mysql> create table DemoTable ( Name varchar(40) ); Query OK, 0 rows affected (0.63 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Chris'); Query OK, 1 row affected (0.22 sec) mysql> insert into DemoTable values('Robert'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('Mike'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('Bob'); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('David'); Query OK, 1 row affected (0.11 sec)Display all records from ...
Read MoreHow to speed up SELECT DISTINCT in MySQL
To speed up SELECT DISTINCT, you can create an index on the column or set of columns. Let us first create a table −mysql> create table DemoTable ( Name varchar(40) ); Query OK, 0 rows affected (1.13 sec)Following is the query to create an index −mysql> create index Name_Index on DemoTable(Name); Query OK, 0 rows affected (1.56 sec) Records: 0 Duplicates: 0 Warnings: 0Insert some records in the table using insert command −mysql> insert into DemoTable values('Chris'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('Mike'); Query OK, 1 row affected (0.15 sec) mysql> insert into ...
Read MoreMySQL query to calculate the total amount from column values with Cost and Quantity?
Let us first create a table −mysql> create table DemoTable ( Cost int, Quantity int ); Query OK, 0 rows affected (0.80 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(65, 2); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable values(290, 4); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values(40, 3); Query OK, 1 row affected (0.10 sec)Display all records from the table using select statement −mysql> select *from DemoTable;This will produce the following output −+------+----------+ | Cost | Quantity | +------+----------+ | 65 ...
Read MoreMySQL query to check if a string contains a word?
For this, you can use the LIKE operator along with CONCAT() function. Let us first create a table −mysql> create table DemoTable ( Value text ); Query OK, 0 rows affected (0.63 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('MySQL'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('Is'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values('Relational'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('Database'); Query OK, 1 row affected (0.13 sec)Display all records from the table using select statement −mysql> select ...
Read MoreHow to select all the records except a row with certain id from a MySQL table?
To avoid displaying a certain id from a table, you need to use the operator, which is the NOT EQUAL operator. Let us first create a table −mysql> create table DemoTable7 ( StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, StudentName varchar(40) ); Query OK, 0 rows affected (0.53 sec)Insert some records in the table using insert command −mysql> insert into DemoTable7(StudentName) values('Chris'); Query OK, 1 row affected (0.25 sec) mysql> insert into DemoTable7(StudentName) values('Robert'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable7(StudentName) values('Mike'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable7(StudentName) ...
Read MoreHow to update empty string to NULL in MySQL?
For this, use LENGTH(), since if the length is 0 that would mean the string is empty. After finding, you can set it to NULL using the SET clause in the UPDATE command. Let us first create a table −mysql> create table DemoTable ( Name varchar(50) ); Query OK, 0 rows affected (0.68 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Chris'); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values(''); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('David'); Query OK, 1 row affected (0.12 sec) mysql> ...
Read MoreGet the first 10 rows followed by the syntax to display remaining row records with a single MySQL query
Let us first create a table −mysql> create table DemoTable ( Id int ); Query OK, 0 rows affected (0.71 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(100); Query OK, 1 row affected (0.31 sec) mysql> insert into DemoTable values(101); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable values(102); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values(103); Query OK, 1 row affected (0.64 sec) mysql> insert into DemoTable values(104); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values(105); Query OK, 1 row affected ...
Read MoreMySQL query to display the first alphabet from strings in a separate column
To fetch the first alphabet from the strings, use LEFT(). This method allows you to return characters from the left of the string.Let us first see an example and create a table −mysql> create table DemoTable ( Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, FirstName varchar(100) ); Query OK, 0 rows affected (1.03 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(FirstName) values('John'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(FirstName) values('Adam'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable(FirstName) values('Jace'); Query OK, 1 row affected (0.16 sec) ...
Read MoreMySQL query to select three highest values and sort alphabetically on the basis of corresponding column with name
For this, you can use the ORDER BY clause. Let us first create a table −mysql> create table DemoTable ( Name varchar(40), Score int ); Query OK, 0 rows affected (1.11 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('Chris', 45); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable values('Bob', 98); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values('David', 78); Query OK, 1 row affected (0.17 sec) mysql> insert into DemoTable values('Mike', 96); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values('Carol', 43); ...
Read MoreAdding records with REPLACE INTO to mimic DELETE and INSERT
You can use REPLACE INTO that works like DELETE + INSERT. Let us first create a table −mysql> create table DemoTable ( Id int, FirstName varchar(50) ); Query OK, 0 rows affected (0.60 sec)Following is the query to create a unique index −mysql> alter table DemoTable add unique id_index(Id); Query OK, 0 rows affected (0.41 sec) Records: 0 Duplicates: 0 Warnings: 0Insert some records in the table using insert command. Since we have added duplicate records, the new record gets added i.e. replaced with the same Id with the previous record −mysql> replace into DemoTable values(100, 'Chris'); Query ...
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