From 18657a960e125336f704ea058e25c27bd3900dcb Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 5 May 2024 19:28:19 +0200 Subject: Adding upstream version 3.40.1. Signed-off-by: Daniel Baumann --- www/c3ref/stmt_readonly.html | 173 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 173 insertions(+) create mode 100644 www/c3ref/stmt_readonly.html (limited to 'www/c3ref/stmt_readonly.html') diff --git a/www/c3ref/stmt_readonly.html b/www/c3ref/stmt_readonly.html new file mode 100644 index 0000000..1a68404 --- /dev/null +++ b/www/c3ref/stmt_readonly.html @@ -0,0 +1,173 @@ + + + + + +Determine If An SQL Statement Writes The Database + + + +
+ + + +
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+Small. Fast. Reliable.
Choose any three. +
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+

SQLite C Interface

 +

Determine If An SQL Statement Writes The Database

+
+
+int sqlite3_stmt_readonly(sqlite3_stmt *pStmt);
+
+

+The sqlite3_stmt_readonly(X) interface returns true (non-zero) if +and only if the prepared statement X makes no direct changes to +the content of the database file.

+ +

Note that application-defined SQL functions or +virtual tables might change the database indirectly as a side effect. +For example, if an application defines a function "eval()" that +calls sqlite3_exec(), then the following SQL statement would +change the database file through side-effects:

+ +

+SELECT eval('DELETE FROM t1') FROM t2;
+

+ +

But because the SELECT statement does not change the database file +directly, sqlite3_stmt_readonly() would still return true.

+ +

Transaction control statements such as BEGIN, COMMIT, ROLLBACK, +SAVEPOINT, and RELEASE cause sqlite3_stmt_readonly() to return true, +since the statements themselves do not actually modify the database but +rather they control the timing of when other statements modify the +database. The ATTACH and DETACH statements also cause +sqlite3_stmt_readonly() to return true since, while those statements +change the configuration of a database connection, they do not make +changes to the content of the database files on disk. +The sqlite3_stmt_readonly() interface returns true for BEGIN since +BEGIN merely sets internal flags, but the BEGIN IMMEDIATE and +BEGIN EXCLUSIVE commands do touch the database and so +sqlite3_stmt_readonly() returns false for those commands.

+ +

This routine returns false if there is any possibility that the +statement might change the database file. A false return does +not guarantee that the statement will change the database file. +For example, an UPDATE statement might have a WHERE clause that +makes it a no-op, but the sqlite3_stmt_readonly() result would still +be false. Similarly, a CREATE TABLE IF NOT EXISTS statement is a +read-only no-op if the table already exists, but +sqlite3_stmt_readonly() still returns false for such a statement.

+ +

If prepared statement X is an EXPLAIN or EXPLAIN QUERY PLAN +statement, then sqlite3_stmt_readonly(X) returns the same value as +if the EXPLAIN or EXPLAIN QUERY PLAN prefix were omitted. +

See also lists of + Objects, + Constants, and + Functions.

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