To update the column size, you can use alter command. The syntax is as follows −alter table yourTableName change yourColumnName yourColumnName data type;To understand the above syntax, let us create a table. The query to create a table −mysql> create table DataTruncated −> ( −> id int, −> Name varchar(5) −> ); Query OK, 0 rows affected (0.64 sec)Look at the column ‘Name’ above, the column size is 5. Whenever we will give the size greater than 5 then MySQL gives the following error −mysql> ... Read More

To get the primary key of a table, you can use the show command. The syntax is as follows −SHOW INDEX FROM yourDatebaseName.yourTableName WHERE Key_name = 'PRIMARY';Suppose, we have a table with two primary keys; one of them is “Id” and second is “RollNum". The query for a table is as follows −mysql> create table TwoOrMorePrimary    −> (    −> Id int,    −> Name varchar(200),    −> RollNum int    −> ,    −> Primary key(Id, Age)    −> ); Query OK, 0 rows affected (0.85 sec)Apply the above syntax to get primary key of a table. ... Read More

Delimiters can be used when you need to define the stored procedures, function as well as to create triggers. The default delimiter is semicolon.You can change the delimiters to create procedures and so on. However, but if you are considering multiple statements, then you need to use different delimiters like $$ or //.Here we have a table “GetRecordFromNow” wherein the following are the records −+---------------------+ | YourDateTime | +---------------------+ | 2018-12-07 22:30:18 | | 2018-12-03 22:30:31 | | 2018-12-02 22:30:41 | | 2018-12-01 22:30:56 | | 2018-12-03 22:31:04 | +---------------------+ 5 rows in ... Read More

To get records from NOW()-1 Day, you can use the following syntax −select *from yourTableName where yourColumnName >=now()-interval 1 day;To understand the above syntax, let us first create a table. The query to create a table.mysql> create table GetRecordsFromNow −> ( −> YourDateTime datetime −> ); Query OK, 0 rows affected (1.76 sec)Now insert some dates into the fields. The query to insert records are as follows −mysql> insert into GetRecordsFromNow values(date_add(now(), interval 3 day)); Query OK, 1 row affected (0.28 sec) mysql> insert into GetRecordsFromNow values(date_add(now(), interval -1 day)); ... Read More

You can change the column position of MySQL table without losing data with the help of ALTER TABLE command. The syntax is as follows −ALTER TABLE yourTableName MODIFY yourColumnName1 data type AFTER yourColumnName2;To understand the above concept, let us create a table. The query to create a table with some columns is as follows −mysql> create table changeColumnPositionDemo −> ( −> StudentId int, −> StudentAddress varchar(200), −> StudentAge int, −> StudentName varchar(200) −> ); Query OK, 0 rows affected (0.72 sec)Let us insert some data in the table. The query to insert records is as follows -.mysql> insert into changeColumnPositionDemo ... Read More

You can search for a string within text column in MySQL with the help of LIKE clause. The syntax is as follows −select *from yourTableName where yourColumnName like '%anyStringValue%';To use the above syntax, let us first create a table −mysql> create table SearchTextDemo    −> (    −> BookName TEXT    −> ); Query OK, 0 rows affected (0.55 sec)Insert some strings in the table. The query is as follows −mysql> insert into SearchTextDemo values('Let us C'); Query OK, 1 row affected (0.28 sec) mysql> insert into SearchTextDemo values('C in Depth'); Query OK, 1 row affected (0.14 sec) ... Read More

To count how many rows have the same value using the function COUNT(*) and GROUP BY. The syntax is as follows −SELECT yourColumName1, count(*) as anyVariableName from yourTableName GROUP BY yourColumName1;To understand the above syntax, let us first create a table. The query to create a table is as follows −mysql> create table RowWithSameValue    −> (    −> StudentId int,    −> StudentName varchar(100),    −> StudentMarks int    −> ); Query OK, 0 rows affected (0.55 sec)Insert some records with same value. Here, we have added same marks for more than one student for our example. The query ... Read More

The equivalent of Java long in the context of MySQL variables is BigInt.In Java, the long datatype takes 8 bytes while BigInt also takes the same number of bytes.Demo of Java longHere is the demo of Java long −public class JavaLongDemo { public static void main(String[]args) { long kilometer = 9223372036854775807L; System.out.println("The largest positive value for long range:"+kilometer); } }The following is the output −Demo of BigIntLet us see an example of BigInt type in MySQL. The following is the query to ... Read More

For random numbers in a range, you need to use the RAND() method from MySQL. The syntax is as follows for update −UPDATE yourTableName set yourColumnName=value where yourColumnName2=(SELECT FLOOR(1+RAND()*3));In the above query, the statement FLOOR(1+RAND()*3) generates the number between 1-3 and update the column.To understand the above syntax, let us first create a table. The query to create a table is as follows −mysql> create table updateRowWith1To3 -> ( -> Id int, -> Name varchar(100) -> ); Query OK, 0 rows affected (0.47 sec)Insert some records in the ... Read More

No, you won’t get any issues with underscores in a MySQL table name. You will get the issues with a dash in a MySQL table name.Here is the demo that does not have any issue with underscore with table names −_StudentTrackerDemoLet us see the same while creating a table. The query to create a table is as follows −mysql> create table _StudentTrackerDemo -> ( -> StudentId int, -> StudentFirstName varchar(100) -> ); Query OK, 0 rows affected (0.75 sec)The underscore is valid for table names but dash is ... Read More