Sql add, delete, modify and check
This section uses knex as the sql framework, taking the sqlite database as an example
Preparation
knex is a framework that runs on the respective database Driver, so you need to install the corresponding js version of the database driver, such as: PostgreSQL -> pg, mysql/mariadb -> mysql, sqlite -> sqlite3…
- Install sqlite3 dependencies
npm install sqlite3 - Install knex dependencies
npm install knex - Introduce dependencies
const app = express();
const knex = require('knex');
- It is recommended to install a suitable database interface tool, the author uses Beekeeper Studio.
create project
Copy the first section of the HelloWorld project
create sqlite connection
Specify the client as sqlite3 (the sqlite3 just installed depends on it), and specify the sqlite database path to be operated
const sqlite = knex({
client: 'sqlite3',
connection: {
filename: './data.db',
},
});
Once a connection instance is created, a connection pool is automatically created, so initializing the database only happens once
connection configuration
The default of sqlite3 is single connection, if you want more connections in the connection pool, bring the pool when creating:
const sqlite = knex({
client: 'sqlite3',
connection: {
filename: './data.db',
},
pool: {
min: 0, max: 7 }
});
Create a connection pool callback
Used to check whether the connection pool is normal, usually this step is not needed
pool: {
afterCreate: function (conn, done) {//...}
}
acquireConnectionTimeout
connection timeout
log
knex has built-in log functions that print warnings, errors, deprecations, and debugging information. If you want to customize log operations, you can override them in the log item
log: {
warn(message) {
},
error(message) {
},
deprecate(message) {
},
debug(message) {
}
}
data sheet
build table
grammar:sqlite.schema.createTable(表名, table=>{表结构})
Add a PUT interface, listen to 127.0.0.1:8080/db/:tbname
and try to create a table according to the table name we want to create. Note: SQL execution is asynchronous. In order to get the result, it is recommended to use async/await syntactic sugar (of course you It’s not bad even if you like hell callbacks)
app.put('/db/:tbname', async function (req, res) {
let resultSet = null;
try {
// Create a table
resultSet = await sqlite.schema
.createTable(req.params.tbname, table => {
table.increments('id');
table.string('uname');
table.string('passwd');
})
// Finally, add a catch statement
} catch(e) {
console.error(e);
resultSet = e;
};
res.json(resultSet);
});
Take a look at the console:
sqlite does not support inserting default values. Set the `useNullAsDefault` flag to hide this warning. (see docs https://knexjs.org/guide/query-builder.html#insert).
Um? sqlite does not support default? Don’t worry about him, go to the database, anyway, the user table is successfully created, if you add useNullAsDefaultthis flag, it will tell you not supported by node-sqlite3
const sqlite = knex({
client: 'sqlite3',
connection: {
filename: './data.db',
},
});
delete table
grammar:sqlite.schema.deleteTable(表名)
app.delete('/db/:tbname', async function (req, res) {
try {
// Delete a table
await sqlite.schema.dropTable(req.params.tbname);
// Finally, add a catch statement
} catch(e) {
console.error(e);
};
res.json(null);
});
table record crud
increase
Insert a new record into the user table
app.use(express.json({
type: 'application/json'}));
app.put('/db/:tbname/record', async function (req, res) {
/*前端请求体格式:
{
"uname": "evanp",
"passwd": "iloveu"
}
*/
let resultSet = null;
try {
// Insert a record
resultSet = await sqlite(req.params.tbname).insert(req.body);
// Finally, add a catch statement
} catch(e) {
console.error(e);
resultSet = e;
};
res.json(resultSet);
});
Try to use the api debugging tool PUT 127.0.0.1:8080/db/user/record, carry the corresponding request body, you will get [1], this is the number of records affected, 1 means success
check
Query uname=the record we just inserted from the user table
app.get('/db/:tbname/record', async function (req, res) {
//前端携带query: uname=evanp
let resultSet = null;
try {
// select a record where uname=xxx
resultSet = await sqlite(req.params.tbname).select('*').where('uname',req.query.uname);
// Finally, add a catch statement
} catch(e) {
console.error(e);
resultSet = e;
};
res.json(resultSet);
});
Try to use the api debugging tool GET 127.0.0.1:8080/db/user/record?uname=evanp, you will get:
[
{
"id": 1,
"uname": "evanp",
"passwd": "iloveu"
}
]
change
Next, we modify the passwd of the uname=evanp record to 123456
app.post('/db/:tbname/record', async function (req, res) {
//前端携带query: uname=evanp
/*前端请求体格式:
{
"passwd": "123456"
}
*/
let resultSet = null;
try {
// select a record where uname=xxx
resultSet = await sqlite(req.params.tbname).update(req.body).where('uname',req.query.uname);
// Finally, add a catch statement
} catch(e) {
console.error(e);
resultSet = e;
};
res.json(resultSet);
});
Try to use the api debugging tool to POST 127.0.0.1:8080/db/user/record?uname=evanp, and carry the corresponding request body, you will get: [1], which means that 1 record is affected, and it is successful
delete
Next, we delete the record of uname=evanp and passwd=123456
app.delete('/db/:tbname/record', async function (req, res) {
/*前端请求体格式:
{
"uname": "evanp",
"passwd": "123456"
}
*/
let resultSet = null;
try {
// select a record where uname=xxx
resultSet = await sqlite(req.params.tbname).del().where(req.body);
// Finally, add a catch statement
} catch(e) {
console.error(e);
resultSet = e;
};
res.json(resultSet);
});
Try to use the api debugging tool DELETE 127.0.0.1:8080/db/user/record, and carry the corresponding request body, you will get: [1], which means 1 affected record, successful
native sql
Of course, if you need to use the sql statement directly, it is also possible, just call it raw(sqlStr), it can be used as a binding of a certain sql, or directly as a whole sql
Format:knex.raw(sql, [bindings]
sqlite.raw("select * from user",[1]).then((resp)=>{
//..})
no introduction here
Summarize
The basic operations of using knex to add, delete, modify and check are given above. These methods are not unique. In actual development, more complex scenarios are often dealt with. The basic crud is far from enough. For more extended use methods of knex,
please Move to knex official documentation https://knexjs.org/guide/