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MySQL Articles
Page 297 of 355
Get the average row length of a MySQL table
In order to get the average row length of a table in MySQL, you can use INFORMATION_SCHEMA.TABLES. Let us first create a table. Following is the query −mysql> create table Client_information -> ( -> Id int, -> Name varchar(10) -> ); Query OK, 0 rows affected (0.48 sec)Following is the query to insert some records in the table using insert command −mysql> insert into Client_information values(1, 'Larry'); Query OK, 1 row affected (0.14 sec) mysql> insert into Client_information values(2, 'Mike'); Query OK, 1 row affected (0.17 sec) mysql> insert into Client_information values(3, 'Sam'); Query ...
Read MoreHow to form a composite key to be unique in MySQL?
To form a composite key to be unique, you need to use ADD UNIQUE command. Following is the syntax −alter table yourTableName add unique yourUniqueName( yourColumnName1, yourColumnName2, .......N);Let us first create a table. Following is the query −mysql> create table makeCompositeKeyDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(40), -> StudentAge int, -> StudentGrade char(1) -> ); Query OK, 0 rows affected (2.34 sec)Now check the description of the table using DESC command. Following is the query −mysql> desc makeCompositeKeyDemo;This will produce the following output −+--------------+-------------+------+-----+---------+----------------+ | Field ...
Read MoreCan we use current_date() for table with column timestamp default in MySQL?
Use the CURRENT_TIMESTAMP instead of current_date() in MySQL for timestamp default current_date. Let us first create a table. Following is the query −mysql> create table defaultCurrent_DateDemo -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(20), -> StudentAdmissionDate timestamp default CURRENT_TIMESTAMP -> ); Query OK, 0 rows affected (0.55 sec)Following is the query to insert some records in the table using insert command −mysql> insert into defaultCurrent_DateDemo(StudentName) values('Larry'); Query OK, 1 row affected (0.52 sec) mysql> insert into defaultCurrent_DateDemo(StudentName, StudentAdmissionDate) values('Chris', '2019-01-31'); Query OK, 1 row affected (0.18 sec)Following is the ...
Read MoreComparing two strings in MySQL?
To compare two strings, which are numbers, let us first create a table. Following is the query −mysql> create table compareTwoStringsDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value varchar(100) -> ); Query OK, 0 rows affected (0.52 sec)Following is the query to insert some records in the table using insert command −mysql> insert into compareTwoStringsDemo(Value) values('1235667'); Query OK, 1 row affected (0.66 sec) mysql> insert into compareTwoStringsDemo(Value) values('999999'); Query OK, 1 row affected (0.11 sec) mysql> insert into compareTwoStringsDemo(Value) values('999888'); Query OK, 1 row affected (0.17 sec) mysql> ...
Read MoreHow to SELECT min and max value from the part of a table in MySQL?
To select min and max value from the part of a table in MySQL, use the following syntax −select min(yourColumnName) as yourAliasName1, max(yourColumnName) as yourAliasName2 from (select yourColumnName from yourTableName limit yourLimitValue) tbl1;Let us first create a table. Following is the query −mysql> create table MinAndMaxValueDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value int -> ); Query OK, 0 rows affected (0.52 sec)Insert records in the table using insert command. Following is the query −mysql> insert into MinAndMaxValueDemo(Value) values(10); Query OK, 1 row affected (0.16 sec) mysql> insert into MinAndMaxValueDemo(Value) ...
Read MoreHow to display some columns (not all) in MySQL?
In order to show some columns, use NOT IN and set those columns which you do not want to display. Let us first create a table. Following is the query −mysql> create table student_Information -> ( -> StudentId int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> StudentName varchar(50), -> StudentAge int, -> StudentAddress varchar(100), -> StudentAllSubjectScore int -> ); Query OK, 0 rows affected (0.69 sec)Following is the query to display a description about the above table −mysql> desc student_Information;This will produce the following output −+------------------------+--------------+------+-----+---------+----------------+ | Field ...
Read MoreMySQL query to get the max value with numeric values in varchar field?
To get the max value, use the max() function. Let us create a table first −mysql> create table findMaxValueInVarcharField -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value varchar(200) -> ); Query OK, 0 rows affected (1.09 sec)Following is the query to insert some records in the table using insert command −mysql> insert into findMaxValueInVarcharField(Value) values('200'); Query OK, 1 row affected (0.14 sec) mysql> insert into findMaxValueInVarcharField(Value) values('1000'); Query OK, 1 row affected (0.25 sec) mysql> insert into findMaxValueInVarcharField(Value) values('899474'); Query OK, 1 row affected (0.18 sec) mysql> insert into ...
Read MoreCheck that a table exists in MySQL?
In order to check a table exists in MySQL, you can use INFORMATION_SCHEMA.TABLES. Let us first create a table −mysql> create table Client_information -> ( -> Id int, -> Name varchar(10) -> ); Query OK, 0 rows affected (0.48 sec)Following is the query to insert some records in the table using insert command −mysql> insert into Client_information values(1, 'Larry'); Query OK, 1 row affected (0.14 sec) mysql> insert into Client_information values(2, 'Mike'); Query OK, 1 row affected (0.17 sec) mysql> insert into Client_information values(3, 'Sam'); Query OK, 1 row affected (0.19 sec)Following is the ...
Read MoreMySQL query to order rows with value greater than zero?
Let us first create a table. Following is the query −mysql> create table gettingAndOrderingRowsDemo -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Value int -> ); Query OK, 0 rows affected (1.35 sec)Following is the query to insert some records in the table using insert command −mysql> insert into gettingAndOrderingRowsDemo(Value) values(10); Query OK, 1 row affected (0.33 sec) mysql> insert into gettingAndOrderingRowsDemo(Value) values(13); Query OK, 1 row affected (0.32 sec) mysql> insert into gettingAndOrderingRowsDemo(Value) values(0); Query OK, 1 row affected (0.17 sec) mysql> insert into gettingAndOrderingRowsDemo(Value) values(20); Query OK, 1 ...
Read MoreMySQL query to display databases sorted by creation date?
You can display databases sorted by creation date with ORDER BY clause. Following is the query to display all databases −mysql> show databases;This will produce the following output −+---------------------------+ | Database | +---------------------------+ | bothinnodbandmyisam | | business | | commandline | | customer_tracker_database | | customertracker | | database1 | | databasesample | | demo ...
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