> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/client-interfaces/ecpg/ecpg-sql-commands/ecpg-sql-prepare.md).

# PREPARE

### PREPARE

PREPARE — prepare a statement for execution

### Synopsis

```

PREPARE prepared_name FROM string
```

### Description

`PREPARE` prepares a statement dynamically specified as a string for execution. This is different from the direct SQL statement [PREPARE](/reference/sql-commands/sql-prepare.md), which can also be used in embedded programs. The [EXECUTE](/reference/sql-commands/sql-execute.md) command is used to execute either kind of prepared statement.

### Parameters

*`prepared_name`* [#](#ECPG-SQL-PREPARE-PREPARED-NAME) : An identifier for the prepared query.

*`string`* [#](#ECPG-SQL-PREPARE-STRING) : A literal string or a host variable containing a preparable SQL statement, one of SELECT, INSERT, UPDATE, or DELETE. Use question marks (`?`) for parameter values to be supplied at execution.

### Notes

In typical usage, the *`string`* is a host variable reference to a string containing a dynamically-constructed SQL statement. The case of a literal string is not very useful; you might as well just write a direct SQL `PREPARE` statement.

If you do use a literal string, keep in mind that any double quotes you might wish to include in the SQL statement must be written as octal escapes (`\042`) not the usual C idiom `\"`. This is because the string is inside an `EXEC SQL` section, so the ECPG lexer parses it according to SQL rules not C rules. Any embedded backslashes will later be handled according to C rules; but `\"` causes an immediate syntax error because it is seen as ending the literal.

### Examples

```

char *stmt = "SELECT * FROM test1 WHERE a = ? AND b = ?";

EXEC SQL ALLOCATE DESCRIPTOR outdesc;
EXEC SQL PREPARE foo FROM :stmt;

EXEC SQL EXECUTE foo USING SQL DESCRIPTOR indesc INTO SQL DESCRIPTOR outdesc;
```

### Compatibility

`PREPARE` is specified in the SQL standard.

### See Also

[EXECUTE](/reference/sql-commands/sql-execute.md)

***

原文：[PostgreSQL 18.6 Documentation](https://www.postgresql.org/docs/18/ecpg-sql-prepare.html)（英文原文，待翻譯）


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