添加sqlx动态查询说明

README.MD

@@ -11,4 +11,121 @@
 
 
 ### note
-- 展开宏：cargo expand --manifest-path .\server\Cargo.toml controller::feedback_controller
+- 展开宏：cargo expand --manifest-path .\server\Cargo.toml controller::feedback_controller
+
+### sql dynamic query
+https://github.com/launchbadge/sqlx/blob/main/FAQ.md#how-can-i-bind-an-array-to-a-values-clause-how-can-i-do-bulk-inserts
+```rust
+use sqlx::{query_builder::QueryBuilder, Execute};
+
+struct Search {
+    id: i64,
+    username: Option<String>,
+    min_age: Option<i8>,
+    max_age: Option<i8>,
+}
+
+fn search_query(search: Search) -> String {
+    let mut query = QueryBuilder::new("SELECT * from users where id = ");
+    query.push_bind(search.id);
+
+    if let Some(username) = search.username {
+        query.push(" AND username = ");
+        query.push_bind(username);
+    }
+
+    if let Some(min_age) = search.min_age {
+        query.push(" AND age > ");
+        query.push_bind(min_age);
+    }
+
+    if let Some(max_age) = search.max_age {
+        query.push(" AND age < ");
+        query.push_bind(max_age);
+    }
+
+    query.build().sql().into()
+}
+
+fn main() {
+    dbg!(search_query(Search {
+        id: 12,
+        username: None,
+        min_age: None,
+        max_age: None,
+    })); // "SELECT * from users where id = $1"
+    dbg!(search_query(Search {
+        id: 12,
+        username: Some("Bob".into()),
+        min_age: None,
+        max_age: None,
+    })); // "SELECT * from users where id = $1 AND username = $2"
+    dbg!(search_query(Search {
+        id: 12,
+        username: Some("Bob".into()),
+        min_age: Some(10),
+        max_age: Some(70),
+    })); // "SELECT * from users where id = $1 AND username = $2 AND age > $3 AND age < $4"
+}
+```
+
+```rust
+use sqlx::{Execute, MySql, QueryBuilder};
+
+struct User {
+    id: i32,
+    username: String,
+    email: String,
+    password: String,
+}
+
+// The number of parameters in MySQL must fit in a `u16`.
+const BIND_LIMIT: usize = 65535;
+
+// This would normally produce values forever!
+let users = (0..).map(|i| User {
+    id: i,
+    username: format!("test_user_{i}"),
+    email: format!("test-user-{i}@example.com"),
+    password: format!("Test!User@Password#{i}"),
+});
+
+let mut query_builder: QueryBuilder<MySql> = QueryBuilder::new(
+    // Note the trailing space; most calls to `QueryBuilder` don't automatically insert
+    // spaces as that might interfere with identifiers or quoted strings where exact
+    // values may matter.
+    "INSERT INTO users(id, username, email, password) "
+);
+
+// Note that `.into_iter()` wasn't needed here since `users` is already an iterator.
+query_builder.push_values(users.take(BIND_LIMIT / 4), |mut b, user| {
+    // If you wanted to bind these by-reference instead of by-value,
+    // you'd need an iterator that yields references that live as long as `query_builder`,
+    // e.g. collect it to a `Vec` first.
+    b.push_bind(user.id)
+        .push_bind(user.username)
+        .push_bind(user.email)
+        .push_bind(user.password);
+});
+
+let mut query = query_builder.build();
+
+// You can then call `query.execute()`, `.fetch_one()`, `.fetch_all()`, etc.
+// For the sake of demonstration though, we're just going to assert the contents
+// of the query.
+
+// These are methods of the `Execute` trait, not normally meant to be called in user code.
+let sql = query.sql();
+let arguments = query.take_arguments().unwrap();
+
+assert!(sql.starts_with(
+    "INSERT INTO users(id, username, email, password) VALUES (?, ?, ?, ?), (?, ?, ?, ?)"
+));
+
+assert!(sql.ends_with("(?, ?, ?, ?)"));
+
+// Not a normally exposed function, only used for this doctest.
+// 65535 / 4 = 16383 (rounded down)
+// 16383 * 4 = 65532
+assert_eq!(arguments.len(), 65532);
+```