Constraints of odoo

There are two ways to implement constraints ：
SQL Constraints are an effective way to ensure data consistency . But if more complex inspections are needed , We need Python constraint .
1、sql constraint
SQL Constraints are defined by model attributes _sql_constraints(name, sql_definition, message).
The following code ：
_sql_constraints = [
(‘code_company_uniq’, ‘unique (code,company_id)’, ‘ Account number must be unique ！’)
]
Realization effect ：

Amount cannot be less than 0 The realization effect of ：

2、python constraint
grammar ：@api.constrains(‘date_end’)
If realized, it shall not be lower than the expected price 90% The effect of the quotation ：

To realize date judgment （ The end date cannot be before today ）, The code is as follows ：

from odoo.exceptions import ValidationError

...

@api.constrains('date_end')
def _check_date_end(self):
    for record in self:
        if record.date_end < fields.Date.today():
            raise ValidationError(" The end date cannot be before today ")
    # all records passed the test, don't return anything

summary ：
SQL Constraints are usually greater than Python Constraints are more effective . When performance is important , I prefer SQL constraint instead of Python constraint .