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Database Articles
Page 369 of 547
How to implement CANDIDATE key in any MySQL table?
Each relation may have one or more candidate key. One of these candidate keys is called Primary Key. Each candidate key qualifies for Primary Key. Therefore, candidates for Primary Key is called Candidate Key. To implement candidate key in MySQL, set more than one column as unique key. These keys would qualify for candidate key as in the below syntax −alter table yourTableName add unique key anyName(yourColumnName1, yourColumnName2);Let us first create a −mysql> create table DemoTable1400 -> ( -> Id int NOT NULL AUTO_INCREMENT PRIMARY KEY, -> Name varchar(40), -> Age int -> ); Query ...
Read MoreGetting the next primary key without adding a new record is impossible, isn't it in MYSQL
No, it is possible to get the next primary key without adding a new record. Let us first create a −mysql> create table DemoTable1399 -> ( -> StudentId int NOT NULL AUTO_INCREMENT, -> PRIMARY KEY(StudentId) -> ); Query OK, 0 rows affected (0.53 sec)Insert some records in the table using insert −mysql> insert into DemoTable1399 values(); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable1399 values(); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1399 values(); Query OK, 1 row affected (0.07 sec)Display all records from the table using select −mysql> select ...
Read MoreFind percentage from marks in MySQL
Let us first create a −mysql> create table DemoTable1398 -> ( -> Marks int -> ); Query OK, 0 rows affected (0.50 sec)Insert some records in the table using insert −mysql> insert into DemoTable1398 values(78); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable1398 values(82); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1398 values(90); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1398 values(98); Query OK, 1 row affected (0.12 sec)Display all records from the table using select −mysql> select * from DemoTable1398;This will produce the following output −+-------+ | ...
Read MoreComparison of varchar date records from the current date in MySQL
For date comparison, you can use STR_TO_DATE(). Following is the syntax −select * from yourTableName where str_to_date(yourColumnName, 'yourFormatSpecifier') > curdate();Let us first create a −mysql> create table DemoTable1397 -> ( -> AdmissionDate varchar(40) -> );s Query OK, 0 rows affected (0.97 sec)Insert some records in the table using insert −mysql> insert into DemoTable1397 values('01/04/2019'); Query OK, 1 row affected (0.11 sec) mysql> insert into DemoTable1397 values('27/09/2019'); Query OK, 1 row affected (0.13 sec) mysql> insert into DemoTable1397 values('29/09/2018'); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1397 values('29/09/2019'); Query OK, 1 row affected (0.08 sec)Display ...
Read MoreMySQL query to sort multiple columns together in a single query
To sort multiple columns, use ORDER BY GREATEST(). Let us first create a −mysql> create table DemoTable1395 -> ( -> Value1 int, -> Value2 int, -> Value3 int -> ); Query OK, 0 rows affected (0.79 sec)Insert some records in the table using insert −mysql> insert into DemoTable1395 values(40, 50, 60); Query OK, 1 row affected (0.14 sec) mysql> insert into DemoTable1395 values(90, 56, 80); Query OK, 1 row affected (0.16 sec) mysql> insert into DemoTable1395 values(10, 20, 30); Query OK, 1 row affected (0.11 sec)Display all records from the table using select −mysql> select ...
Read MoreFormat amount values for thousands number with two decimal places in MySQL?
For thousands number, use MySQL FORMAT(). Let us first create a −mysql> create table DemoTable1394 -> ( -> Amount decimal(7, 3) -> ); Query OK, 0 rows affected (0.68 sec)Insert some records in the table using insert −mysql> insert into DemoTable1394 values(60); Query OK, 1 row affected (0.15 sec) mysql> insert into DemoTable1394 values(2355.4); Query OK, 1 row affected (0.27 sec) mysql> insert into DemoTable1394 values(456); Query OK, 1 row affected (0.12 sec) mysql> insert into DemoTable1394 values(8769); Query OK, 1 row affected (0.13 sec)Display all records from the table using select −mysql> select * from DemoTable1394;This ...
Read MoreMySQL pattern matching 3 or more "a's" in name?
Following is the syntax −select * from yourTableName where yourColumnName like '%a%a%a%';Let us first create a −mysql> create table DemoTable1393 -> ( -> CountryName varchar(40) -> ); Query OK, 0 rows affected (0.71 sec)Insert some records in the table using insert −mysql> insert into DemoTable1393 values('andorra'); Query OK, 1 row affected (0.50 sec) mysql> insert into DemoTable1393 values('australia'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1393 values('argentina'); Query OK, 1 row affected (0.46 sec) mysql> insert into DemoTable1393 values('austria'); Query OK, 1 row affected (0.26 sec)Display all records from the table using select −mysql> ...
Read MoreMySQL query to fetch date more recent than 14 days?
Let us first create a −mysql> create table DemoTable1392 -> ( -> ArrivalDate date -> ); Query OK, 0 rows affected (0.43 sec)Insert some records in the table using insert −mysql> insert into DemoTable1392 values('2019-09-10'); Query OK, 1 row affected (0.46 sec) mysql> insert into DemoTable1392 values('2019-09-26'); Query OK, 1 row affected (0.09 sec) mysql> insert into DemoTable1392 values('2019-09-12'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1392 values('2018-09-20'); Query OK, 1 row affected (0.31 sec) mysql> insert into DemoTable1392 values('2019-10-11'); Query OK, 1 row affected (0.11 sec)Display all records from the table using select ...
Read MoreFix error in MySQL "select ClientId,ClientName,ClientAge, from tablename
The error occurs because we have a comma at the end of the column names, just before “from tablename’. Here is the error you may have got −mysql> select ClientId, ClientName, ClientAge, from DemoTable1391; ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'from DemoTable1391' at line 1To remove the error, as discussed above, you need to remove the last comma from the table. Let us first create a −mysql> create table DemoTable1391 -> ( -> ClientId int NOT ...
Read MoreMySQL automatic string to integer casting in WHERE clause to fetch a specific id
If the string begins with integer then it converts the string to integer, otherwise it won’t. Let us first create a −mysql> create table DemoTable1390 -> ( -> StudentId varchar(20) -> ); Query OK, 0 rows affected (0.93 sec)Insert some records in the table using insert −mysql> insert into DemoTable1390 values('563_John'); Query OK, 1 row affected (0.10 sec) mysql> insert into DemoTable1390 values('1001_Carol_Taylor'); Query OK, 1 row affected (0.08 sec) mysql> insert into DemoTable1390 values('David_Miller_789'); Query OK, 1 row affected (0.07 sec) mysql> insert into DemoTable1390 values('456_AdamSmith'); Query OK, 1 row affected (0.11 sec)Display all records from ...
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