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Articles by Sharon Christine
Page 13 of 34
How to update multiple rows and left pad values in MySQL?
Use the LPAD() function to left pad values. Let us first create a table −mysql> create table DemoTable -> ( -> Number int -> ); Query OK, 0 rows affected (2.26 secInsert some records in the table using insert command −mysql> insert into DemoTable values(857786); Query OK, 1 row affected (0.26 sec) mysql> insert into DemoTable values(89696); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values(89049443); Query OK, 1 row affected (0.25 secDisplay all records from the table using select statement −mysql> select *from DemoTable;OutputThis will produce the following output −+----------+ | ...
Read MoreFind and display duplicate values only once from a column in MySQL
Let us first create a table −mysql> create table DemoTable -> ( -> value int -> ); Query OK, 0 rows affected (0.82 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(10); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(100); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable values(20); Query OK, 1 row affected (0.28 sec) mysql> insert into DemoTable values(10); Query OK, 1 row affected (0.34 sec) mysql> insert into DemoTable values(30); Query OK, 1 row affected (0.24 sec) mysql> insert into ...
Read MoreIf I truncate a table, should I also add indexes?
If you truncate a table, you do not need to add indexes because table is recreated after truncating a table and indexes get added automatically.Let us first create a table −mysql> create table DemoTable -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> FirstName varchar(20), -> LastName varchar(20) -> ); Query OK, 0 rows affected (0.65 sec)Following is the query to create an index −mysql> create index Index_firstName_LastName on DemoTable(FirstName, LastName); Query OK, 0 rows affected (1.04 sec) Records: 0 Duplicates: 0 Warnings: 0Insert some records in the table using insert command −mysql> ...
Read MoreMySQL query to return a substring after delimiter?
Use SUBSTRING() to return values after delimiter. Let us first create a table −mysql> create table DemoTable -> ( -> Title text -> ); Query OK, 0 rows affected (0.56 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('John is good in MySQL, Sam is good in MongoDB, Mike is good in Java'); Query OK, 1 row affected (0.19 sec)Display all records from the table using select statement −mysql> select *from DemoTable;OutputThis will produce the following output −+-------------------------------------------------------------------+ | Title ...
Read MoreAdding integers from a variable to a MySQL column?
To set a variable, use MySQL SET. For adding integers from a variable, use UPDATE and SET as in the below syntax −set @anyVariableName:=yourValue; update yourTableName set yourColumnName=yourColumnName+ @yourVariableName;Let us first create a table −mysql> create table DemoTable -> ( -> Number int -> ); Query OK, 0 rows affected (0.68 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(10); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values(20); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable values(40); Query OK, 1 row affected (0.15 sec) mysql> ...
Read MoreIs it impossible to add a column in MySQL specifically before another column?
No, you can easily add a column before another column using ALTER.Note − To add a column at a specific position within a table row, use FIRST or AFTER col_name Let us first create a table −mysql> create table DemoTable -> ( -> Id int, -> Name varchar(20), -> CountryName varchar(100) -> ); Query OK, 0 rows affected (0.67 sec)Let us check all the column names from the table −mysql> show columns from DemoTable;OutputThis will produce the following output −+-------------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key ...
Read MoreMySQL XOR operator with IN clause?
MySQL XOR returns TRUE if one or the other operand (or expression) but not both is TRUE. The IN clause is used to specify a condition with any other MySQL query.Let us first create a tablemysql> create table DemoTable -> ( -> Num1 int, -> Num2 int -> ); Query OK, 0 rows affected (0.61 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(5, 5); Query OK, 1 row affected (0.19 sec) mysql> insert into DemoTable values(6, 6); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values(7, 7); Query OK, ...
Read MoreDisplay records from two columns based on comparison in MySQL?
Let us first create a table −mysql> create table DemoTable -> ( -> Num1 int, -> Num2 int -> ); Query OK, 0 rows affected (0.54 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(100, 200); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(200, 100); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(300, 400); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values(400, 300); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values(500, 600); Query OK, 1 ...
Read MoreCount only null values in two different columns and display in one MySQL select statement?
Use IS NULL to test for NULL value. Let us first create a table −mysql> create table DemoTable -> ( -> Number1 int, -> Number2 int -> ); Query OK, 0 rows affected (0.62 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(1, NULL); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable values(NULL, NULL); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values(3, NULL); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable values(NULL, 90); Query OK, 1 row affected ...
Read MoreChange multiple columns in a single MySQL query?
For this, use UPDATE and REPLACE() in MySQL. Let us first create a table −mysql> create table DemoTable -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(100), -> StudentCountryName varchar(100) -> ); Query OK, 0 rows affected (0.67 sec)Insert some records in the table using insert command −mysql> insert into DemoTable(StudentName, StudentCountryName) values('John', 'US'); Query OK, 1 row affected (0.15 sec)Display all records from the table using select statement −mysql select *from DemoTable;OutputThis will produce the following output −+-----------+-------------+--------------------+ | StudentId | StudentName | StudentCountryName | +-----------+-------------+--------------------+ | ...
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