And the common function MySQL- CRUD

Insert data INSERT

1. Insert character and date data

Character and date data should be included in single quotes

INSERT INTO departments (department_id, department_name, manager_id,location_id) 
VALUES (280, 'PR', 100, 1700)

possible problems

1. Foreign key value table and the value of the field where the foreign key does not match a field into the data. eg: job_idThe table is a foreign key, a value inserted SA_RAPin to job_idthe table's primary key jobsis not present in.

• The exception clause

INSERT INTO
employees(employee_id, last_name, email, hiredate, job_id)
VALUES (302, 'DDX', '[email protected]', STR_TO_DATE('2019-1-1','%Y-%m-%d'), 'SA_RAP')

• Exception information

Cannot add or update a child row: a foreign key constraint fails (`myemployees`.`employees`, CONSTRAINT `job_id_fk` FOREIGN KEY (`job_id`) REFERENCES `jobs` (`job_id`))

2. Insert the null value

Implicit Insert: omitted values for the column name in the list

INSERT INTO departments (department_id, department_name  ) 
VALUES (290, 'PR')

Explicit inserted in VALUESspecified null

INSERT INTO departments 
VALUES (300, 'PR', NULL, NULL)

Modify (update) data UPDATE

• WHEREClause specifies the data to be updated, if omitted WHERERclause, all data in the table is updated.
• A plurality of data can be updated, if prior to roll back the data, the operation is performed to set SET AUTOCOMMIT = FALSE.

UPDATE employees
SET department_id = 70
WHERE employee_id = 113

delete data DELETE

• WHEREClause specifies the record to be deleted.

DELETE FROM departments
WHERE departments.department_name = 'Finance'

Common Functions

1. Character Functions

• Case-control function
  

• Character control function
  

2. Digital function

Rounding, truncating decimal places, modulo

3. Date Functions

Gets the current date string into a date, the date is converted to a string

Date functions common format control character