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The reset the primary key of a table means to reset the auto_increment property to 1. The syntax is as follows to reset the primary key of a table.alter table yourTableName auto_increment = 1;To understand, let us create a table −mysql> create table ResetPrimaryKey −> ( −> Id int auto_increment, −> PRIMARY KEY(Id) −> ); Query OK, 0 rows affected (0.59 sec)Insert some records into the table. The query to insert records is as follows −mysql> insert into ResetPrimaryKey values(); Query OK, 1 row affected (0.18 sec) mysql> insert into ResetPrimaryKey values(); Query OK, 1 row affected ... Read More
You can change table engine with the help of alter command. The syntax is as follows −alter table yourTableName ENGINE = yourEngineName;To understand the above syntax let us create a table with engine MyISAM. Later you can change any other engine. The following is the query to create a table.mysql> create table ChangeEngineTableDemo −> ( −> MovieId int, −> MovieName varchar(100), −> IsPopular bool −> )ENGINE = 'MyISAM'; Query OK, 0 rows affected (0.37 sec)Look at the above query, the table engine is MyISAM, now you can change it to any other engine. Here, we will change ... Read More
You can get timestamp with the help of current_timestamp, now() and current_timestamp().Case 1 − Using current_timestamp()The query is as follows −mysql> SELECT CURRENT_TIMESTAMP();The following is the output displaying timestamp −+---------------------+ | CURRENT_TIMESTAMP() | +---------------------+ | 2018-11-29 16:09:31 | +---------------------+ 1 row in set (0.00 sec)Case 2 − Using now()The query is as follows −mysql> select now();The following is the output −+---------------------+ | now() | +---------------------+ | 2018-11-29 16:09:38 | +---------------------+ 1 row in set (0.00 sec)You can get integer UNIX timestamp with the help of below query −mysql> select unix_timestamp();The following is the ... Read More
Use the STR_TO_DATE() function from MySQL to set a date format for displaying DD/MM/YYYY date. The syntax is as follows −SELECT STR_TO_DATE(yourColumnName, ’%d/%m/%Y) as anyVariableName from yourTableName.To understand the above syntax, let us create a table −mysql> create table DateFormatDemo −> ( −> IssueDate varchar(100) −> ); Query OK, 0 rows affected (0.54 sec)Inserting some string dates into the table. The query to insert date is as follows −mysql> insert into DateFormatDemo values('26/11/2018'); Query OK, 1 row affected (0.14 sec) mysql> insert into DateFormatDemo values('27/11/2018'); Query OK, 1 row affected (0.18 sec) mysql> ... Read More
To list all triggers in a MySQL database, you can use the SHOW command. The query is as follows −mysql> show triggers;The following is the output −+----------------+--------+----------------------+--------------------------------------------------------------------+--------+------------------------+--------------------------------------------+---------+----------------------+----------------------+--------------------+ | Trigger | Event | Table | Statement | Timing | Created | sql_mode ... Read More
To cast DATETIME as a DATE in MySQL, use the CAST() function. The syntax is as follows −select cast(yourColumnName as Date) as anyVariableName from yourTableName;To understand the above syntax, let us first create a table −mysql> create table ConvertDatetimeToDate −> ( −> YourDatetime datetime −> ); Query OK, 0 rows affected (0.95 sec)Inserting datetime into the table with the help of insert command. The query is as follows −mysql> insert into ConvertDatetimeToDate values(date_add(now(), interval 1 day)); Query OK, 1 row affected (0.17 sec) mysql> insert into ConvertDatetimeToDate values(date_add(now(), interval -1 day)); Query OK, 1 row affected (0.15 sec) ... Read More
You can use SHOW VARIABLES command to display current configuration variables. The syntax is as follows −SHOW VARIABLES;If you want any specific information, then implement the LIKE operator. The syntax is as follows −SHOW VARIABLES LIKE ‘%AnySpecificInformation%’;Now we will implement the above syntax −mysql> show variables like '%variable%';The following is the output −+--------------------------------+------------------------------------------------------------------------------------------+ | Variable_name | Value ... Read More
To get the number of columns, use the aggregate function count(*) with information_schema table from MySQL. The syntax is as follows to find the number of columns −SELECT COUNT(*) as anyVariableName from INFORMATION_SCHEMA.COLUMNS where table_schema = ’yourDatabaseName’ and table_name = ’yourTableName’;To understand the above syntax, let us create a table with some columns. The following is the query to create a table −mysql> create table CountColumns −> ( −> Bookid int, −> BookName varchar(200), −> BookAuthorName varchar(200), −> BookPublishedDate datetime −> ); Query OK, 0 rows affected (0.69 sec)Now, we have total 4 columns in my ... Read More
You can set primary key on an existing column in MySQL with the help of alter command.The syntax is as follows to add primary key to an existing column.ALTER TABLE yourTableName ADD PRIMARY KEY(yourColumnName);To set existing column as primary key, let us first create a table. The query to create a table −mysql> create table AddingPrimaryKeyDemo −> ( −> UniversityId int, −> UniversityName varchar(200) −> ); Query OK, 0 rows affected (1.16 sec)Look at the above query, I haven’t added primary key. Let us check the same with the help of DESC ... Read More
You can move rows from one table to another with the help of INSERT INTO SELECT statement.The syntax is as follows −insert into yourDestinationTableName select *from yourOriginalTable where someConditionTo understand the above syntax. let us create a table. The following is the query to create a table −mysql> create table StudentTable −> ( −> Id int, −> Name varchar(100) −> ); Query OK, 0 rows affected (0.65 sec)Now, I will create second table. The query is as follows −mysql> create table Employee −> ( −> EmployeeId int ... Read More