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Database Articles
Page 228 of 547
If 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 MoreMySQL query to conduct a basic search for a specific last name in a column
You can use LIKE operator to conduct a basic search for last name. Let us first create a table: −mysql> create table DemoTable -> ( -> CustomerName varchar(100), -> CustomerAge int -> ); Query OK, 0 rows affected (0.77 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('John Doe', 34); Query OK, 1 row affected (1.32 sec) mysql> insert into DemoTable values('David Miller', 24); Query OK, 1 row affected (0.18 sec) mysql> insert into DemoTable values('Bob Doe', 27); Query OK, 1 row affected (0.18 sec) mysql> insert into ...
Read MoreCalling NOW() function to fetch current date records in MySQL?
Let us first create a table −mysql> create table DemoTable -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> ShippingDate datetime -> ); Query OK, 0 rows affected (1.16 sec)Insert some records in the table using insert command. Consider current date “2019-06-28” −mysql> insert into DemoTable(ShippingDate) values('2019-01-31'); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable(ShippingDate) values('2019-06-06'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable(ShippingDate) values('2019-06-28'); Query OK, 1 row affected (0.20 sec) mysql> insert into DemoTable(ShippingDate) values('2019-07-01'); Query OK, 1 row affected (0.16 sec)Display all records from the table ...
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 MoreCan we use ORDER BY NULL in MySQL?
Yes, we can do thatNote − Before MySQL 5.7, ORDER BY NULL was useful, but with MySQL 8.0, specifying ORDER BY NULL, for example, at the end to suppress implicit sorting is no longer necessary.Let us first create a table −mysql> create table DemoTable -> ( -> Name varchar(10) -> ); Query OK, 0 rows affected (1.01 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values('John'); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable values('Bob'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values('David'); Query OK, 1 ...
Read MoreSort a column in descending order after placing argument in MySQL IN()?
For this, use FIELD() function with DESC. Let us first create a table −mysql> create table DemoTable -> ( -> Number int -> ); Query OK, 0 rows affected (0.57 sec)Insert some records in the table using insert command −mysql> insert into DemoTable values(10); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable values(20); Query OK, 1 row affected (0.27 sec) mysql> insert into DemoTable values(30); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable values(40); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable values(50); Query OK, 1 row ...
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 ...
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